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Versions: (draft-onedm-t2trg-sdf) 00 01 02 03 04         Standards Track
          05 06 07 08 09                                                
ASDF                                                      M. Koster, Ed.
Internet-Draft                                              PassiveLogic
Intended status: Standards Track                         C. Bormann, Ed.
Expires: 28 April 2022                            Universität Bremen TZI
                                                         25 October 2021


  Semantic Definition Format (SDF) for Data and Interactions of Things
                         draft-ietf-asdf-sdf-08

Abstract

   The Semantic Definition Format (SDF) is a format for domain experts
   to use in the creation and maintenance of data and interaction models
   in the Internet of Things.  It was created as a common language for
   use in the development of the One Data Model liaison organization
   (OneDM) definitions.  Tools convert this format to database formats
   and other serializations as needed.

   An SDF specification describes definitions of SDF Objects and their
   associated interactions (Events, Actions, Properties), as well as the
   Data types for the information exchanged in those interactions.


   // A JSON format representation of SDF 1.0 was defined in version
   // (-00) of this document; version (-05) was designated as an
   // _implementation draft_, labeled SDF 1.1, at the IETF110 meeting of
   // the ASDF WG (2021-03-11).  The present version (-08) adds URIs as
   // alternative measurement unit names, is editorially more self-
   // contained, and uses updated xml2rfc conventions for its plain-text
   // rendering.

Contributing

   Recent versions of this document are available at its GitHub
   repository https://github.com/ietf-wg-asdf/SDF (https://github.com/
   ietf-wg-asdf/SDF) -- this also provides an issue tracker as well as a
   way to supply "pull requests".

   General discussion of this SDF Internet-Draft happens on the mailing
   list of the IETF ASDF Working Group, asdf@ietf.org (subscribe at
   https://www.ietf.org/mailman/listinfo/asdf
   (https://www.ietf.org/mailman/listinfo/asdf)).

   The IETF Note Well applies (https://www.ietf.org/about/note-well/
   (https://www.ietf.org/about/note-well/)).





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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 28 April 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Terminology and Conventions . . . . . . . . . . . . . . .   4
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Example Definition  . . . . . . . . . . . . . . . . . . .   6
     2.2.  Elements of an SDF model  . . . . . . . . . . . . . . . .   8
       2.2.1.  sdfObject . . . . . . . . . . . . . . . . . . . . . .   9
       2.2.2.  sdfProperty . . . . . . . . . . . . . . . . . . . . .  10
       2.2.3.  sdfAction . . . . . . . . . . . . . . . . . . . . . .  11
       2.2.4.  sdfEvent  . . . . . . . . . . . . . . . . . . . . . .  11
       2.2.5.  sdfData . . . . . . . . . . . . . . . . . . . . . . .  12
       2.2.6.  sdfThing  . . . . . . . . . . . . . . . . . . . . . .  12
       2.2.7.  sdfProduct  . . . . . . . . . . . . . . . . . . . . .  12
   3.  SDF structure . . . . . . . . . . . . . . . . . . . . . . . .  12
     3.1.  Information block . . . . . . . . . . . . . . . . . . . .  13
     3.2.  Namespaces section  . . . . . . . . . . . . . . . . . . .  14



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     3.3.  Definitions section . . . . . . . . . . . . . . . . . . .  15
   4.  Names and namespaces  . . . . . . . . . . . . . . . . . . . .  16
     4.1.  Structure . . . . . . . . . . . . . . . . . . . . . . . .  16
     4.2.  Contributing global names . . . . . . . . . . . . . . . .  16
     4.3.  Referencing global names  . . . . . . . . . . . . . . . .  17
     4.4.  sdfRef  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     4.5.  sdfRequired . . . . . . . . . . . . . . . . . . . . . . .  19
     4.6.  Common Qualities  . . . . . . . . . . . . . . . . . . . .  20
     4.7.  Data Qualities  . . . . . . . . . . . . . . . . . . . . .  21
       4.7.1.  sdfType . . . . . . . . . . . . . . . . . . . . . . .  23
       4.7.2.  sdfChoice . . . . . . . . . . . . . . . . . . . . . .  24
   5.  Keywords for definition groups  . . . . . . . . . . . . . . .  26
     5.1.  sdfObject . . . . . . . . . . . . . . . . . . . . . . . .  26
     5.2.  sdfProperty . . . . . . . . . . . . . . . . . . . . . . .  27
     5.3.  sdfAction . . . . . . . . . . . . . . . . . . . . . . . .  27
     5.4.  sdfEvent  . . . . . . . . . . . . . . . . . . . . . . . .  28
     5.5.  sdfData . . . . . . . . . . . . . . . . . . . . . . . . .  28
   6.  High Level Composition  . . . . . . . . . . . . . . . . . . .  28
     6.1.  Paths in the model namespaces . . . . . . . . . . . . . .  29
     6.2.  Modular Composition . . . . . . . . . . . . . . . . . . .  29
       6.2.1.  Use of the "sdfRef" keyword to re-use a definition  .  30
     6.3.  sdfThing  . . . . . . . . . . . . . . . . . . . . . . . .  31
     6.4.  sdfProduct  . . . . . . . . . . . . . . . . . . . . . . .  31
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
     7.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  32
     7.2.  Registries  . . . . . . . . . . . . . . . . . . . . . . .  32
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  32
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  33
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  33
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  34
   Appendix A.  Formal Syntax of SDF . . . . . . . . . . . . . . . .  35
   Appendix B.  json-schema.org Rendition of SDF Syntax  . . . . . .  39
   Appendix C.  Data Qualities inspired by json-schema.org . . . . .  78
     C.1.  type "number", type "integer" . . . . . . . . . . . . . .  79
     C.2.  type "string" . . . . . . . . . . . . . . . . . . . . . .  79
     C.3.  type "boolean"  . . . . . . . . . . . . . . . . . . . . .  80
     C.4.  type "array"  . . . . . . . . . . . . . . . . . . . . . .  80
     C.5.  type "object" . . . . . . . . . . . . . . . . . . . . . .  80
     C.6.  Implementation notes  . . . . . . . . . . . . . . . . . .  81
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  81
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  81
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  82









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1.  Introduction

   The Semantic Definition Format (SDF) is a format for domain experts
   to use in the creation and maintenance of data and interaction models
   in the Internet of Things.  It was created as a common language for
   use in the development of the One Data Model liaison organization
   (OneDM) definitions.  Tools convert this format to database formats
   and other serializations as needed.

   An SDF specification describes definitions of SDF Objects and their
   associated interactions (Events, Actions, Properties), as well as the
   Data types for the information exchanged in those interactions.


   // A JSON format representation of SDF 1.0 was defined in version
   // (-00) of this document; version (-05) was designated as an
   // _implementation draft_, labeled SDF 1.1, at the IETF110 meeting of
   // the ASDF WG (2021-03-11).  The present version (-08) adds URIs as
   // alternative measurement unit names, is editorially more self-
   // contained, and uses updated xml2rfc conventions for its plain-text
   // rendering.

1.1.  Terminology and Conventions

   Thing:  A physical item that is also made available in the Internet
      of Things.  The term is used here for Things that are notable for
      their interaction with the physical world beyond interaction with
      humans; a temperature sensor or a light might be a Thing, but a
      router that employs both temperature sensors and indicator lights
      might exhibit less Thingness, as the effects of its functioning
      are mostly on the digital side.

   Affordance:  An element of an interface offered for interaction,
      defining its possible uses or making clear how it can or should be
      used.  The term is used here for the digital interfaces of a Thing
      only; it might also have physical affordances such as buttons,
      dials, and displays.

   Quality:  A metadata item in a definition or declaration which says
      something about that definition or declaration.  A quality is
      represented in SDF as an entry in a JSON map (object) that serves
      as a definition or declaration.

   Entry:  A key-value pair in a map.  (In JSON maps, sometimes also
      called "member".)

   Block:  One or more entries in a JSON map that is part of an SDF
      specification; these entries together serve a specific function.



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   Group:  An entry in the main SDF map and in certain nested
      definitions that has a Class Name Keyword as its key and a map of
      definition entries (Definition Group) as a value.

   Class Name Keyword:  One of sdfThing, sdfProduct, sdfObject,
      sdfProperty, sdfAction, sdfEvent, or sdfData; the Classes for
      these type keywords are capitalized and prefixed with sdf.

   Class:  Abstract term for the information that is contained in groups
      identified by a Class Name Keyword.

   Property:  An affordance that can potentially be used to read, write,
      and/or observe state on an Object.  (Note that Entries are often
      called properties in other environments; in this document, the
      term Property is specifically reserved for affordances, even if
      the map key "properties" might be imported from a data definition
      language with the other semantics.)

   Action:  An affordance that can potentially be used to perform a
      named operation on an Object.

   Event:  An affordance that can potentially be used to obtain
      information about what happened to an Object.

   Object:  A grouping of Property, Action, and Event definitions; the
      main "atom" of reusable semantics for model construction.  (Note
      that JSON maps are often called JSON objects due to JSON's
      JavaScript heritage; in this document, the term Object is
      specifically reserved for the above grouping, even if the type
      name "object" might be imported from a data definition language
      with the other semantics.)

   Element:  A part or an aspect of something abstract; used here in its
      usual English definition.  (Occasionally, also used specifically
      for the elements of JSON arrays.)

   Definition:  An entry in a Definition Group; the entry creates a new
      semantic term for use in SDF models and associates it with a set
      of qualities.

   Declaration:  A reference to and a use of a definition within an
      enclosing definition, intended to create component instances
      within that enclosing definition.  Every declaration can also be
      used as a definition for reference in a different place.

   Protocol Binding:  A companion document to an SDF specification that





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      defines how to map the abstract concepts in the specification into
      the protocols in use in a specific ecosystem.  Might supply URL
      components, numeric IDs, and similar details.

   The term "byte" is used in its now-customary sense as a synonym for
   "octet".

   Conventions:

   *  The singular form is chosen as the preferred one for the keywords
      defined here.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Overview

2.1.  Example Definition

   We start with an example for the SDF definition of a simple Object
   called "Switch" (Figure 1).



























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   {
       "info": {
           "title": "Example file for OneDM Semantic Definition Format",
           "version": "2019-04-24",
           "copyright": "Copyright 2019 Example Corp. All rights reserved.",
           "license": "https://example.com/license"
       },
       "namespace": {
           "cap": "https://example.com/capability/cap"
       },
       "defaultNamespace": "cap",
       "sdfObject": {
           "Switch": {
               "sdfProperty": {
                   "value": {
                       "description": "The state of the switch; false for off and true for on.",
                       "type": "boolean"
                   }
               },
               "sdfAction": {
                   "on": {
                       "description": "Turn the switch on; equivalent to setting value to true."
                   },
                   "off": {
                       "description": "Turn the switch off; equivalent to setting value to false."
                   },
                   "toggle": {
                       "description": "Toggle the switch; equivalent to setting value to its complement."
                   }
               }
           }
       }
   }

            Figure 1: A simple example of an SDF definition file

   This is a model of a switch.  The state value declared in the
   sdfProperty group, represented by a Boolean, will be true for "on"
   and will be false for "off".  The actions on or off declared in the
   sdfAction group are redundant with setting the value and are in the
   example to illustrate that there are often different ways of
   achieving the same effect.  The action toggle will invert the value
   of the sdfProperty value, so that 2-way switches can be created;
   having such action will avoid the need for first retrieving the
   current value and then applying/setting the inverted value.






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   The sdfObject group lists the affordances of instances of this
   object.  The sdfProperty group lists the property affordances
   described by the model; these represent various perspectives on the
   state of the object.  Properties can have additional qualities to
   describe the state more precisely.  Properties can be annotated to be
   read, write or read/write; how this is actually done by the
   underlying transfer protocols is not described in the SDF model but
   left to companion protocol bindings.  Properties are often used with
   RESTful paradigms [I-D.irtf-t2trg-rest-iot], describing state.  The
   sdfAction group is the mechanism to describe other interactions in
   terms of their names, input, and output data (no data are used in the
   example), as in a POST method in REST or in a remote procedure call.
   The example toggle is an Action that changes the state based on the
   current state of the Property named value.  (The third type of
   affordance is Events, which are not described in this example.)

   In the JSON representation, note how (with the exception of the info
   group) maps that have keys taken from the SDF vocabulary (info,
   namespace, sdfObject) alternate in nesting with maps that have keys
   that are freely defined by the model writer (Switch, value, on,
   etc.); the latter usually use the named<> production in the formal
   syntax of SDF (Appendix A), while the former SDF-defined vocabulary
   items are often, but not always, called _qualities_.

2.2.  Elements of an SDF model

   The SDF language uses seven predefined Class Name Keywords for
   modeling connected Things, six of which are illustrated in Figure 2
   (the seventh class sdfProduct is similar enough to sdfThing that it
   would look the same in the figure).





















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                   ,--------.
                   |sdfThing|
                   |--------|
                   `--------'
                        |
                        |
                  ,---------.
                  |sdfObject|
                  |---------|
                  `---------'
                        |
   ,-----------.  ,---------.   ,--------.
   |sdfProperty|  |sdfAction|   |sdfEvent|
   |-----------|  |---------|   |--------|
   `-----------'  `---------'   `--------'
                       |

                   ,-------.
                   |sdfData|
                   |-------|
                   `-------'

                 Figure 2: Main classes used in SDF models

   The seven main Class Name Keywords are discussed below.

2.2.1.  sdfObject

   Objects, the items listed in an sdfObject group, are the main "atom"
   of reusable semantics for model construction.  It aligns in scope
   with common definition items from many IoT modeling systems, for
   example ZigBee Clusters [ZCL], OMA SpecWorks LwM2M Objects [OMA], and
   OCF Resource Types [OCF].

   An sdfObject contains a set of sdfProperty, sdfAction, and sdfEvent
   definitions that describe the interaction affordances associated with
   some scope of functionality.

   For the granularity of definition, sdfObject definitions are meant to
   be kept narrow enough in scope to enable broad reuse and
   interoperability.  For example, defining a light bulb using separate
   sdfObject definitions for on/off control, dimming, and color control
   affordances will enable interoperable functionality to be configured
   for diverse product types.  An sdfObject definition for a common on/
   off control may be used to control may different kinds of Things that
   require on/off control.





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   Optional qualities "minItems" and "maxItems" can be used to define
   sdfObjects as arrays.

2.2.2.  sdfProperty

   sdfProperty is used to model elements of state within sdfObject
   instances.

   An instance of sdfProperty may be associated with some protocol
   affordance to enable the application to obtain the state variable
   and, optionally, modify the state variable.  Additionally, some
   protocols provide for in-time reporting of state changes.  (These
   three aspects are described by the qualities readable, writable, and
   observable defined for an sdfProperty.)

   Definitions in sdfProperty groups look like definitions in sdfData
   groups, however, they actually also declare a Property with the given
   qualities to be potentially present in the containing Object.
   (Qualities beyond those of sdfData definitions could be defined for
   sdfProperty declarations but currently aren't; this means that even
   Property qualities such as readable and writable can be associated
   with definitions in sdfData groups, as well.)

   For definitions in sdfProperty and sdfData, SDF provides qualities
   that can constrain the structure and values of data allowed in an
   instance of these data, as well as qualities that associate semantics
   to these data, for engineering units and unit scaling information.

   For the data definition within sdfProperty or sdfData, SDF borrows
   some vocabulary proposed for the drafts 4 and 7 of the json-
   schema.org "JSON Schema" format (collectively called JSO here),
   enhanced by qualities that are specific to SDF.  Details about the
   former are in Appendix C.  For the current version of SDF, data are
   constrained to be of simple types (number, string, Boolean), JSON
   maps composed of named data ("objects"), and arrays of these types.
   Syntax extension points are provided that can be used to provide
   richer types in future versions of this specification (possibly more
   of which can be borrowed from json-schema.org).

   Note that sdfProperty definitions (and sdfData definitions in
   general) are not intended to constrain the formats of data used for
   communication over network interfaces.  Where needed, data
   definitions for payloads of protocol messages are expected to be part
   of the protocol binding.







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2.2.3.  sdfAction

   The sdfAction group contains declarations of Actions, model
   affordances that, when triggered, have more effect than just reading,
   updating, or observing Thing state, often resulting in some outward
   physical effect (which, itself, cannot be modeled in SDF).  From a
   programmer's perspective, they might be considered to be roughly
   analogous to method calls.

   Actions may have data parameters; these are modeled as a single item
   of input data and output data, each.  (Where multiple parameters need
   to be modeled, an "object" type can be used to combine these
   parameters into one.)  Actions may be long-running, that is to say
   that the effects may not take place immediately as would be expected
   for an update to an sdfProperty; the effects may play out over time
   and emit action results.  Actions may also not always complete and
   may result in application errors, such as an item blocking the
   closing of an automatic door.

   Actions may have (or lack) qualities of idempotency and side-effect
   safety.

   The current version of SDF only provides data constraint modeling and
   semantics for the input and output data of definitions in sdfAction
   groups.  Again, data definitions for payloads of protocol messages,
   and detailed protocol settings for invoking the action, are expected
   to be part of the protocol binding.

2.2.4.  sdfEvent

   The sdfEvent group contains declarations of Events, which can model
   affordances that inform about "happenings" associated with an
   instance of an Object; these may result in a signal being stored or
   emitted as a result.

   Note that there is a trivial overlap with sdfProperty state changes,
   which may also be defined as events but are not generally required to
   be defined as such.  However, Events may exhibit certain ordering,
   consistency, and reliability requirements that are expected to be
   supported in various implementations of sdfEvent that do distinguish
   sdfEvent from sdfProperty.  For instance, while a state change may
   simply be superseded by another state change, some events are
   "precious" and need to be preserved even if further events follow.








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   The current version of SDF only provides data constraint modeling and
   semantics for the output data of Event affordances.  Again, data
   definitions for payloads of protocol messages, and detailed protocol
   settings for invoking the action, are expected to be part of the
   protocol binding.

2.2.5.  sdfData

   Definitions in sdfData groups are provided separately from those in
   sdfProperty groups to enable common modeling patterns, data
   constraints, and semantic anchor concepts to be factored out for data
   items that make up sdfProperty items and serve as input and output
   data for sdfAction and sdfEvent items.

   It is a common use case for such a data definition to be shared
   between an sdfProperty item and input or output parameters of an
   sdfAction or output data provided by an sdfEvent. sdfData definitions
   also enable factoring out extended application data types such as
   mode and machine state enumerations to be reused across multiple
   definitions that have similar basic characteristics and requirements.

2.2.6.  sdfThing

   Back at the top level, the sdfThing groups enables definition of
   models for complex devices that will use one or more sdfObject
   definitions.

   A definition in an sdfThing group can refine the metadata of the
   definitions it is composed from: other definitions in sdfThing groups
   definitions in sdfObject groups.

2.2.7.  sdfProduct

   sdfThing has a derived class sdfProduct, which can be used to
   indicate a top level inventory item with a Stock-Keeping Unit (SKU)
   identifier and other particular metadata.  Structurally, there is no
   difference between definitions in either group; semantically, a
   definition in an sdfProduct group is intended to describe a class of
   complete Things.

3.  SDF structure

   SDF definitions are contained in SDF files.  One or more SDF files
   can work together to provide the definitions and declarations that
   are the payload of the SDF format.






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   A SDF definition file contains a single JSON map (JSON object).  This
   object has three sections: the information block, the namespaces
   section, and the definitions section.

3.1.  Information block

   The information block contains generic meta data for the file itself
   and all included definitions.  To enable tool integration, the
   information block is optional in the grammar of SDF; most processes
   for working with SDF files will have policies that only SDF models
   with an info block can be processed.  It is therefore RECOMMENDED
   that SDF validator tools emit a warning when no information block is
   found.

   The keyword (map key) that defines an information block is "info".
   Its value is a JSON map in turn, with a set of entries that represent
   qualities that apply to the included definition.

   Qualities of the information block are shown in Table 1.

    +===========+========+==========+=================================+
    | Quality   | Type   | Required | Description                     |
    +===========+========+==========+=================================+
    | title     | string | yes      | A short summary to be displayed |
    |           |        |          | in search results, etc.         |
    +-----------+--------+----------+---------------------------------+
    | version   | string | yes      | The incremental version of the  |
    |           |        |          | definition, format TBD          |
    +-----------+--------+----------+---------------------------------+
    | copyright | string | yes      | Link to text or embedded text   |
    |           |        |          | containing a copyright notice   |
    +-----------+--------+----------+---------------------------------+
    | license   | string | yes      | Link to text or embedded text   |
    |           |        |          | containing license terms        |
    +-----------+--------+----------+---------------------------------+

                Table 1: Qualities of the Information Block

   While the format of the version string is marked as TBD, it is
   intended to be lexicographically increasing over the life of a model:
   a newer model always has a version string that string-compares higher
   than all previous versions.  This is easily achieved by following the
   convention to start the version with an [RFC3339] date-time or, if
   new versions are generated less frequently than once a day, just the
   full-date (i.e., YYYY-MM-DD); in many cases, that will be all that is
   needed (see Figure 1 for an example).





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   The license string is preferably either a URI that points to a web
   page with an unambiguous definition of the license, or an [SPDX]
   license identifier.  (For models to be handled by the One Data Model
   liaison group, this will typically be "BSD-3-Clause".)

3.2.  Namespaces section

   The namespaces section contains the namespace map and the
   defaultNamespace setting.

   The namespace map is a map from short names for URIs to the namespace
   URIs themselves.

   The defaultNamespace setting selects one of the entries in the
   namespace map by giving its short name.  The associated URI (value of
   this entry) becomes the default namespace for the SDF definition
   file.

     +==================+========+==========+=======================+
     | Quality          | Type   | Required | Description           |
     +==================+========+==========+=======================+
     | namespace        | map    | no       | Defines short names   |
     |                  |        |          | mapped to namespace   |
     |                  |        |          | URIs, to be used as   |
     |                  |        |          | identifier prefixes   |
     +------------------+--------+----------+-----------------------+
     | defaultNamespace | string | no       | Identifies one of the |
     |                  |        |          | prefixes in the       |
     |                  |        |          | namespace map to be   |
     |                  |        |          | used as a default in  |
     |                  |        |          | resolving identifiers |
     +------------------+--------+----------+-----------------------+

                       Table 2: Namespaces Section

   The following example declares a set of namespaces and defines cap as
   the default namespace.  By convention, the values in the namespace
   map contain full URIs without a fragment identifier, and the fragment
   identifier is then added, if needed, where the namespace entry is
   used.

   "namespace": {
     "cap": "https://example.com/capability/cap",
     "zcl": "https://zcl.example.com/sdf"
   },
   "defaultNamespace": "cap",





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   If no defaultNamespace setting is given, the SDF definition file does
   not contribute to a global namespace.  As the defaultNamespace is set
   by giving a namespace short name, its presence requires a namespace
   map that contains a mapping for that namespace short name.

   If no namespace map is given, no short names for namespace URIs are
   set up, and no defaultNamespace can be given.

3.3.  Definitions section

   The Definitions section contains one or more groups, each identified
   by a Class Name Keyword (there can only be one group per keyword; the
   actual grouping is just a shortcut and does not carry any specific
   semantics).  The value of each group is a JSON map (object), the keys
   of which serve for naming the individual definitions in this group,
   and the corresponding values provide a set of qualities (name-value
   pairs) for the individual definition.  (In short, we speak of the map
   entries as "named sets of qualities".)

   Each group may contain zero or more definitions.  Each identifier
   defined creates a new type and term in the target namespace.
   Declarations have a scope of the current definition block.

   A definition may in turn contain other definitions.  Each definition
   is a named set of qualities, i.e., it consists of the newly defined
   identifier and a set of key-value pairs that represent the defined
   qualities and contained definitions.

   An example for an Object definition is given in Figure 3:

   "sdfObject": {
     "foo": {
       "sdfProperty": {
         "bar": {
           "type": "boolean"
         }
       }
     }
   }

                    Figure 3: Example Object definition

   This example defines an Object "foo" that is defined in the default
   namespace (full address: #/sdfObject/foo), containing a property that
   can be addressed as #/sdfObject/foo/sdfProperty/bar, with data of
   type boolean.





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   Some of the definitions are also declarations: the definition of the
   entry "bar" in the property "foo" means that each instance of a "foo"
   can have zero or one instance of a "bar".  Entries within
   sdfProperty, sdfAction, and sdfEvent, within sdfObject entries, are
   declarations.  Similarly, entries within an sdfThing describe
   instances of sdfObject (or nested sdfThing) that form part of
   instances of the Thing.

4.  Names and namespaces

   SDF definition files may contribute to a global namespace, and may
   reference elements from that global namespace.  (An SDF definition
   file that does not set a defaultNamespace does not contribute to a
   global namespace.)

4.1.  Structure

   Global names look exactly like https:// URIs with attached fragment
   identifiers.

   There is no intention to require that these URIs can be dereferenced.
   (However, as future versions of SDF might find a use for
   dereferencing global names, the URI should be chosen in such a way
   that this may become possible in the future.)

   The absolute URI of a global name should be a URI as per Section 3 of
   [RFC3986], with a scheme of "https" and a path (hier-part in
   [RFC3986]).  For the present version of this specification, the query
   part should not be used (it might be used in later versions).

   The fragment identifier is constructed as per Section 6 of [RFC6901].

4.2.  Contributing global names

   The fragment identifier part of a global name defined in an SDF
   definition file is constructed from a JSON pointer that selects the
   element defined for this name in the SDF definition file.

   The absolute URI part is a copy of the default namespace, i.e., the
   default namespace is always the target namespace for a name for which
   a definition is contributed.  When emphasizing that name definitions
   are contributed to the default namespace, we therefore also call it
   the "target namespace" of the SDF definition file.

   E.g., in Figure 1, definitions for the following global names are
   contributed:

   *  https://example.com/capability/cap#/sdfObject/Switch



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   *  https://example.com/capability/cap#/sdfObject/Switch/sdfProperty/
      value

   *  https://example.com/capability/cap#/sdfObject/Switch/sdfAction/on

   *  https://example.com/capability/cap#/sdfObject/Switch/sdfAction/off

   Note the #, which separates the absolute-URI part (Section 4.3 of
   [RFC3986]) from the fragment identifier part.

4.3.  Referencing global names

   A name reference takes the form of the production curie in
   [W3C.NOTE-curie-20101216] (note that this excludes the production
   safe-curie), but also limiting the IRIs involved in that production
   to URIs as per [RFC3986] and the prefixes to ASCII characters
   [RFC0020].

   A name that is contributed by the current SDF definition file can be
   referenced by a Same-Document Reference as per section 4.4 of
   [RFC3986].  As there is little point in referencing the entire SDF
   definition file, this will be a # followed by a JSON pointer.  This
   is the only kind of name reference to itself that is possible in an
   SDF definition file that does not set a default namespace.

   Name references that point outside the current SDF definition file
   need to contain curie prefixes.  These then reference namespace
   declarations in the namespaces section.

   For example, if a namespace prefix is defined:

   "namespace": {
     "foo": "https://example.com/"
   }

   Then this reference to that namespace:

   { "sdfRef": "foo:#/sdfData/temperatureData" }

   references the global name:

   "https://example.com/#/sdfData/temperatureData"

   Note that there is no way to provide a URI scheme name in a curie, so
   all references outside of the document need to go through the
   namespace map.

   Name references occur only in specific elements of the syntax of SDF:



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   *  copying elements via sdfRef values

   *  pointing to elements via sdfRequired value elements

4.4.  sdfRef

   In a JSON map establishing a definition, the keyword "sdfRef" is used
   to copy all of the qualities of the referenced definition, indicated
   by the included name reference, into the newly formed definition.
   (This can be compared to the processing of the "$ref" keyword in
   [I-D.handrews-json-schema-validation].)

   For example, this reference:

   "temperatureProperty": {
     "sdfRef": "#/sdfData/temperatureData"
   }

   creates a new definition "temperatureProperty" that contains all of
   the qualities defined in the definition at /sdfData/temperatureData.

   The sdfRef member need not be the only member of a map.  Additional
   members may be present with the intention to override parts of the
   referenced map.  More formally, for a JSON map that contains an
   sdfRef member, the semantics is defined to be as if the following
   steps were performed:

   1.  The JSON map that contains the sdfRef member is copied into a
       variable named "patch".

   2.  The sdfRef member of the copy in "patch" is removed.

   3.  the JSON pointer that is the value of the sdfRef member is
       dereferenced and the result is copied into a variable named
       "original".

   4.  The JSON Merge Patch algorithm [RFC7396] is applied to patch the
       contents of "original" with the contents of "patch".

   5.  The result of the Merge Patch is used in place of the value of
       the original JSON map.

   TODO: Make sure that the grammar in Appendix A allows specifying the
   null values that are necessary to remove members in a merge-patch.







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4.5.  sdfRequired

   The keyword "sdfRequired" is provided to apply a constraint that
   defines for which declarations corresponding data are mandatory in an
   instance conforming the current definition.

   The value of "sdfRequired" is an array of name references (JSON
   pointers), each indicating one declaration that is mandatory to be
   represented.

   The example in Figure 4 shows two required elements in the sdfObject
   definition for "temperatureWithAlarm", the sdfProperty
   "currentTemperature", and the sdfEvent "overTemperatureEvent".  The
   example also shows the use of JSON pointer with "sdfRef" to use a
   pre-existing definition in this definition, for the "alarmType" data
   (sdfOutputData) produced by the sdfEvent "overTemperatureEvent".



































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   {
     "sdfObject": {
       "temperatureWithAlarm": {
         "sdfRequired": [
           "#/sdfObject/temperatureWithAlarm/sdfProperty/currentTemperature",
           "#/sdfObject/temperatureWithAlarm/sdfEvent/overTemperatureEvent"
         ],
         "sdfData":{
           "temperatureData": {
             "type": "number"
           }
         },
         "sdfProperty": {
           "currentTemperature": {
             "sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
           }
         },
         "sdfEvent": {
           "overTemperatureEvent": {
             "sdfOutputData": {
               "type": "object",
               "properties": {
                 "alarmType": {
                   "sdfRef": "cap:#/sdfData/alarmTypes/quantityAlarms",
                   "const": "OverTemperatureAlarm"
                 },
                 "temperature": {
                   "sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
                 }
               }
             }
           }
         }
       }
     }
   }

                        Figure 4: Using sdfRequired

4.6.  Common Qualities

   Definitions in SDF share a number of qualities that provide metadata
   for them.  These are listed in Table 3.  None of these qualities are
   required or have default values that are assumed if the quality is
   absent.  If a label is required for an application and no label is
   given in the SDF model, the last part (reference-token, Section 3 of
   [RFC6901]) of the JSON pointer to the definition can be used.




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    +=============+==============+===================================+
    | Quality     | Type         | Description                       |
    +=============+==============+===================================+
    | description | text         | long text (no constraints)        |
    +-------------+--------------+-----------------------------------+
    | label       | text         | short text (no constraints)       |
    +-------------+--------------+-----------------------------------+
    | $comment    | text         | source code comments only, no     |
    |             |              | semantics                         |
    +-------------+--------------+-----------------------------------+
    | sdfRef      | sdf-pointer  | (see Section 4.4)                 |
    +-------------+--------------+-----------------------------------+
    | sdfRequired | pointer-list | (see Section 4.5, applies to      |
    |             |              | qualities of properties, of data) |
    +-------------+--------------+-----------------------------------+

                        Table 3: Common Qualities

4.7.  Data Qualities

   Data qualities are used in sdfData and sdfProperty definitions, which
   are named sets of data qualities (abbreviated as named-sdq).

   Appendix C lists data qualities inspired by the various proposals at
   json-schema.org; the intention is that these (information model
   level) qualities are compatible with the (data model) semantics from
   the versions of the json-schema.org proposal they were imported from.

   Table 4 lists data qualities defined specifically for the present
   specification.

    +===============+================+======================+=========+
    | Quality       | Type           | Description          | Default |
    +===============+================+======================+=========+
    | (common)      |                | Section 4.6          |         |
    +---------------+----------------+----------------------+---------+
    | unit          | string         | unit name (note 1)   | N/A     |
    +---------------+----------------+----------------------+---------+
    | scaleMinimum  | number         | lower limit of value | N/A     |
    |               |                | in units given by    |         |
    |               |                | unit (note 2)        |         |
    +---------------+----------------+----------------------+---------+
    | scaleMaximum  | number         | upper limit of value | N/A     |
    |               |                | in units given by    |         |
    |               |                | unit (note 2)        |         |
    +---------------+----------------+----------------------+---------+
    | readable      | boolean        | Reads are allowed    | true    |
    +---------------+----------------+----------------------+---------+



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    | writable      | boolean        | Writes are allowed   | true    |
    +---------------+----------------+----------------------+---------+
    | observable    | boolean        | flag to indicate     | true    |
    |               |                | asynchronous         |         |
    |               |                | notification is      |         |
    |               |                | available            |         |
    +---------------+----------------+----------------------+---------+
    | nullable      | boolean        | indicates a null     | true    |
    |               |                | value is available   |         |
    |               |                | for this type        |         |
    +---------------+----------------+----------------------+---------+
    | contentFormat | string         | content type (IANA   | N/A     |
    |               |                | media type string    |         |
    |               |                | plus parameters),    |         |
    |               |                | encoding             |         |
    +---------------+----------------+----------------------+---------+
    | sdfType       | string         | sdfType enumeration  | N/A     |
    |               | (Section       | (extensible)         |         |
    |               | 4.7.1)         |                      |         |
    +---------------+----------------+----------------------+---------+
    | sdfChoice     | named set of   | named alternatives   | N/A     |
    |               | data qualities |                      |         |
    |               | (Section       |                      |         |
    |               | 4.7.2)         |                      |         |
    +---------------+----------------+----------------------+---------+
    | enum          | array of       | abbreviation for     | N/A     |
    |               | strings        | string-valued named  |         |
    |               |                | alternatives         |         |
    +---------------+----------------+----------------------+---------+

         Table 4: SDF-defined Qualities of sdfProperty and sdfData

   1.  Note that the quality unit was called units in SDF 1.0.  The unit
       name SHOULD be as per the SenML Units Registry or the Secondary
       Units Registry in [IANA.senml] as specified by Sections 4.5.1 and
       12.1 of [RFC8428] and Section 3 of [RFC8798], respectively.
       Exceptionally, if a registration in these registries cannot be
       obtained or would be inappropriate, the unit name can also be a
       URI that is pointing to a definition of the unit.  Note that SDF
       processors are not expected to (and normally SHOULD NOT)
       dereference these URIs; they may be useful to humans, though.  A
       URI unit name is distinguished from a registered unit name by the
       presence of a colon; registered unit names that contain a colon
       (at the time of writing, none) can therefore not be used in SDF.







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   2.  these qualities were included in SDF 1.0, but were not fully
       defined; they are not included in SDF 1.1.  In 1.next, they will
       be replaced by qualities to express scaling that are more aligned
       with the processes that combine ecosystem and instance specific
       information with an SDF model.

4.7.1.  sdfType

   SDF defines a number of basic types beyond those provided by JSON or
   JSO.  These types are identified by the sdfType quality, which is a
   text string from a set of type names defined by SDF.

   To aid interworking with [I-D.handrews-json-schema-validation]
   implementations, it is RECOMMENDED that sdfType is always used in
   conjunction with the type quality inherited from
   [I-D.handrews-json-schema-validation], in such a way as to yield a
   common representation of the type's values in JSON.

   Values for sdfType that are defined in SDF 1.1 are shown in Table 5.
   This table also gives a description of the semantics of the sdfType,
   the conventional value for type to be used with the sdfType value,
   and a conventional JSON representation for values of the type.

     +=============+=============+========+==========================+
     | sdfType     | Description | type   | JSON Representation      |
     +=============+=============+========+==========================+
     | byte-string | A sequence  | string | base64url without        |
     |             | of zero or  |        | padding (Section 3.4.5.2 |
     |             | more bytes  |        | of [RFC8949])            |
     +-------------+-------------+--------+--------------------------+
     | unix-time   | A point in  | number | POSIX time               |
     |             | civil time  |        | (Section 3.4.2 of        |
     |             | (note 1)    |        | [RFC8949])               |
     +-------------+-------------+--------+--------------------------+

           Table 5: Values defined in SDF 1.1 for sdfType quality

   (1) Note that the definition of unix-time does not imply the
   capability to represent points in time that fall on leap seconds.
   More date/time-related sdfTypes are likely to be added in future
   versions of this specification.

   In SDF 1.0, a similar concept was called subtype.








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4.7.2.  sdfChoice

   Data can be a choice of named alternatives, called sdfChoice.  Each
   alternative is identified by a name (string, key in the JSON object
   used to represent the choice) and a set of dataqualities (object, the
   value in the JSON object used to represent the choice).

   sdfChoice merges the functions of two constructs found in
   [I-D.handrews-json-schema-validation]:

   *  enum

      What would have been

      "enum": ["foo", "bar", "baz"]

      in SDF 1.0, is often best represented as:

      "sdfChoice": {
        "foo": { "description": "This is a foonly"},
        "bar": { "description": "As defined in the second world congress"},
        "baz": { "description": "From zigbee foobaz"}
      }

      This allows the placement of other dataqualities such as
      description in the example.

      If an enum needs to use a data type different from text string,
      e.g. what would have been

      "type": "number",
      "enum": [1, 2, 3]

      in SDF 1.0, is represented as:

      "type": "number",
      "sdfChoice": {
        "a-better-name-for-alternative-1": { "const": 1 },
        "alternative-2": { "const": 2 },
        "the-third-alternative": { "const": 3 }
      }

      where the string names obviously would be chosen in a way that is
      descriptive for what these numbers actually stand for; sdfChoice
      also makes it easy to add number ranges into the mix.






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      (Note that const can also be used for strings as in the previous
      example, e.g., if the actual string value is indeed a crucial
      element for the data model.)

   *  anyOf

      [I-D.handrews-json-schema-validation] provides a type union called
      anyOf, which provides a choice between anonymous alternatives.

      What could have been

      "anyOf": [
        {"type": "array", "minItems": 3, "maxItems": "3", "items": {
           "sdfRef": "#/sdfData/rgbVal"}}
        {"type": "array", "minItems": 4, "maxItems": "4", "items": {
           "sdfRef": "#/sdfData/cmykVal"}}
      ]

      in [I-D.handrews-json-schema-validation] can be more descriptively
      notated in SDF as:

      "sdfChoice": {
        "rgb": {"type": "array", "minItems": 3, "maxItems": "3", "items": {
                  "sdfRef": "#/sdfData/rgbVal"}},
        "cmyk": {"type": "array", "minItems": 4, "maxItems": "4", "items": {
                  "sdfRef": "#/sdfData/cmykVal"}}
      }

   Note that there is no need in SDF for the type intersection construct
   allOf or the peculiar type-xor construct oneOf found in
   [I-D.handrews-json-schema-validation].

   As a simplification for readers of SDF specifications accustomed to
   the [I-D.handrews-json-schema-validation] enum keyword, this is
   retained, but limited to a choice of text string values, such that

   "enum": ["foo", "bar", "baz"]

   is syntactic sugar for

   "sdfChoice": {
     "foo": { "const": "foo"},
     "bar": { "const": "bar"},
     "baz": { "const": "baz"}
   }






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5.  Keywords for definition groups

   The following SDF keywords are used to create definition groups in
   the target namespace.  All these definitions share some common
   qualities as discussed in Section 4.6.

5.1.  sdfObject

   The sdfObject keyword denotes a group of zero or more Object
   definitions.  Object definitions may contain or include definitions
   of Properties, Actions, Events declared for the object, as well as
   data types (sdfData group) to be used in this or other Objects.

   The qualities of an sdfObject include the common qualities,
   additional qualities are shown in Table 6.  None of these qualities
   are required or have default values that are assumed if the quality
   is absent.

         +=============+===========+=============================+
         | Quality     | Type      | Description                 |
         +=============+===========+=============================+
         | (common)    |           | Section 4.6                 |
         +-------------+-----------+-----------------------------+
         | sdfProperty | property  | zero or more named property |
         |             |           | definitions for this object |
         +-------------+-----------+-----------------------------+
         | sdfAction   | action    | zero or more named action   |
         |             |           | definitions for this object |
         +-------------+-----------+-----------------------------+
         | sdfEvent    | event     | zero or more named event    |
         |             |           | definitions for this object |
         +-------------+-----------+-----------------------------+
         | sdfData     | named-sdq | zero or more named data     |
         |             |           | type definitions that might |
         |             |           | be used in the above        |
         +-------------+-----------+-----------------------------+
         | minItems    | number    | (array) Minimum number of   |
         |             |           | sdfObject instances in      |
         |             |           | array                       |
         +-------------+-----------+-----------------------------+
         | maxItems    | number    | (array) Maximum number of   |
         |             |           | sdfObject instances in      |
         |             |           | array                       |
         +-------------+-----------+-----------------------------+

                      Table 6: Qualities of sdfObject





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5.2.  sdfProperty

   The sdfProperty keyword denotes a group of zero or more Property
   definitions.

   Properties are used to model elements of state.

   The qualities of a Property definition include the data qualities
   (and thus the common qualities), see Section 4.7.

5.3.  sdfAction

   The sdfAction keyword denotes a group of zero or more Action
   definitions.

   Actions are used to model commands and methods which are invoked.
   Actions have parameter data that are supplied upon invocation.

   The qualities of an Action definition include the common qualities,
   additional qualities are shown in Table 7.

        +===============+===========+============================+
        | Quality       | Type      | Description                |
        +===============+===========+============================+
        | (common)      |           | Section 4.6                |
        +---------------+-----------+----------------------------+
        | sdfInputData  | map       | data qualities of the      |
        |               |           | input data for an Action   |
        +---------------+-----------+----------------------------+
        | sdfOutputData | map       | data qualities of the      |
        |               |           | output data for an Action  |
        +---------------+-----------+----------------------------+
        | sdfData       | named-sdq | zero or more named data    |
        |               |           | type definitions that      |
        |               |           | might be used in the above |
        +---------------+-----------+----------------------------+

                     Table 7: Qualities of sdfAction

   sdfInputData defines the input data of the action.  sdfOutputData
   defines the output data of the action.  As discussed in
   Section 2.2.3, a set of data qualities with type "object" can be used
   to substructure either data item, with optionality indicated by the
   data quality required.







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5.4.  sdfEvent

   The sdfEvent keyword denotes zero or more Event definitions.

   Events are used to model asynchronous occurrences that may be
   communicated proactively.  Events have data elements which are
   communicated upon the occurrence of the event.

   The qualities of sdfEvent include the common qualities, additional
   qualities are shown in Table 8.

        +===============+===========+============================+
        | Quality       | Type      | Description                |
        +===============+===========+============================+
        | (common)      |           | Section 4.6                |
        +---------------+-----------+----------------------------+
        | sdfOutputData | map       | data qualities of the      |
        |               |           | output data for an Event   |
        +---------------+-----------+----------------------------+
        | sdfData       | named-sdq | zero or more named data    |
        |               |           | type definitions that      |
        |               |           | might be used in the above |
        +---------------+-----------+----------------------------+

                      Table 8: Qualities of sdfEvent

   sdfOutputData defines the output data of the action.  As discussed in
   Section 2.2.4, a set of data qualities with type "object" can be used
   to substructure the output data item, with optionality indicated by
   the data quality required.

5.5.  sdfData

   The sdfData keyword denotes a group of zero or more named data type
   definitions (named-sdq).

   An sdfData definition provides a reusable semantic identifier for a
   type of data item and describes the constraints on the defined type.
   It is not itself a declaration, i.e., it does not cause any of these
   data items to be included in an affordance definition.

   The qualities of sdfData include the data qualities (and thus the
   common qualities), see Section 4.7.

6.  High Level Composition

   The requirements for high level composition include the following:




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   *  The ability to represent products, standardized product types, and
      modular products while maintaining the atomicity of Objects.

   *  The ability to compose a reusable definition block from Objects,
      for example a single plug unit of an outlet strip with on/off
      control, energy monitor, and optional dimmer objects, while
      retaining the atomicity of the individual objects.

   *  The ability to compose Objects and other definition blocks into a
      higher level thing that represents a product, while retaining the
      atomicity of objects.

   *  The ability to enrich and refine a base definition to have
      product-specific qualities and quality values, e.g. unit, range,
      and scale settings.

   *  The ability to reference items in one part of a complex definition
      from another part of the same definition, for example to summarize
      the energy readings from all plugs in an outlet strip.

6.1.  Paths in the model namespaces

   The model namespace is organized according to terms that are defined
   in the definition files that are present in the namespace.  For
   example, definitions that originate from an organization or vendor
   are expected to be in a namespace that is specific to that
   organization or vendor.  There is expected to be an SDF namespace for
   common SDF definitions used in OneDM.

   The structure of a path in a namespace is defined by the JSON
   Pointers to the definitions in the files in that namespace.  For
   example, if there is a file defining an object "Switch" with an
   action "on", then the reference to the action would be
   "ns:/sdfObject/Switch/sdfAction/on" where ns is the namespace prefix
   (short name for the namespace).

6.2.  Modular Composition

   Modular composition of definitions enables an existing definition
   (could be in the same file or another file) to become part of a new
   definition by including a reference to the existing definition within
   the model namespace.









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6.2.1.  Use of the "sdfRef" keyword to re-use a definition

   An existing definition may be used as a template for a new
   definition, that is, a new definition is created in the target
   namespace which uses the defined qualities of some existing
   definition.  This pattern will use the keyword "sdfRef" as a quality
   of a new definition with a value consisting of a reference to the
   existing definition that is to be used as a template.

   In the definition that uses "sdfRef", new qualities may be added and
   existing qualities from the referenced definition may be overridden.
   (Note that JSON maps (objects) do not have a defined order, so the
   SDF processor may see these overrides before seeing the sdfRef.)

   As a convention, overrides are intended to be used only for further
   restricting the set of data values, as shown in Figure 5: any value
   for a cable-length also is a valid value for a length, with the
   additional restriction that the length cannot be smaller than 5 cm.
   (This is labeled as a convention as it cannot be checked in the
   general case; a quality of implementation consideration for a tool
   might be to provide at least some form of checking.)  Note that a
   description is provided that overrides the description of the
   referenced definition; as this quality is intended for human
   consumption there is no conflict with the intended goal.

   "sdfData":
     "length" : {
       "type": "number",
       "minimum": 0,
       "unit": "m"
       "description": "There can be no negative lengths."
     }
   ...
     "cable-length" : {
       "sdfRef": "#/sdfData/length"
       "minimum": 0.05,
       "description": "Cables must be at least 5 cm."
     }

                                  Figure 5











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6.3.  sdfThing

   An sdfThing is a set of declarations and qualities that may be part
   of a more complex model.  For example, the object declarations that
   make up the definition of a single socket of an outlet strip could be
   encapsulated in an sdfThing, and the socket-thing itself could be
   used in a declaration in the sdfThing definition for the outlet
   strip.

   sdfThing definitions carry semantic meaning, such as a defined
   refrigerator compartment and a defined freezer compartment, making up
   a combination refrigerator-freezer product.

   An sdfThing may be composed of sdfObjects and other sdfThings.

   The qualities of sdfThing are shown in Table 9.

                   +===========+========+=============+
                   | Quality   | Type   | Description |
                   +===========+========+=============+
                   | (common)  |        | Section 4.6 |
                   +-----------+--------+-------------+
                   | sdfThing  | thing  |             |
                   +-----------+--------+-------------+
                   | sdfObject | object |             |
                   +-----------+--------+-------------+

                      Table 9: Qualities of sdfThing
                              and sdfProduct

6.4.  sdfProduct

   An sdfProduct provides the level of abstraction for representing a
   unique product or a profile for a standardized type of product, for
   example a "device type" definition with required minimum
   functionality.

   Products may be composed of Objects and Things at the high level, and
   may include their own definitions of Properties, Actions, and Events
   that can be used to extend or complete the included Object
   definitions.

   Product definitions may set optional defaults and constant values for
   specific use cases, for example units, range, and scale settings for
   properties, or available parameters for Actions.

   The qualities of sdfProduct are the same as for sdfThing and are
   shown in Table 9.



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7.  IANA Considerations

7.1.  Media Type

   IANA is requested to add the following Media-Type to the "Media
   Types" registry.

   +==========+======================+=======================+
   | Name     | Template             | Reference             |
   +==========+======================+=======================+
   | sdf+json | application/sdf+json | RFC XXXX, Section 7.1 |
   +----------+----------------------+-----------------------+

                             Table 10

   // RFC Ed.: please replace RFC XXXX with this RFC number and remove
   this note.

   Type name:  application
   Subtype name:  sdf+json
   Required parameters:  none
   Optional parameters:  none
   Encoding considerations:  binary (JSON is UTF-8-encoded text)
   Security considerations:  Section 8 of RFC XXXX
   Interoperability considerations:  none
   Published specification:  Section 7.1 of RFC XXXX
   Applications that use this media type:  Tools for data and
      interaction modeling in the Internet of Things
   Fragment identifier considerations:  A JSON Pointer fragment
      identifier may be used, as defined in Section 6 of [RFC6901].
   Person & email address to contact for further information:  ASDF WG
      mailing list (asdf@ietf.org), or IETF Applications and Real-Time
      Area (art@ietf.org)
   Intended usage:  COMMON
   Restrictions on usage:  none
   Author/Change controller:  IETF
   Provisional registration:  no

7.2.  Registries

   (TBD: After future additions, check if we need any.)

8.  Security Considerations

   Some wider issues are discussed in [RFC8576].

   (Specifics: TBD.)




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9.  References

9.1.  Normative References

   [I-D.ietf-cbor-cddl-control]
              Bormann, C., "Additional Control Operators for CDDL", Work
              in Progress, Internet-Draft, draft-ietf-cbor-cddl-control-
              07, 21 October 2021, <https://www.ietf.org/archive/id/
              draft-ietf-cbor-cddl-control-07.txt>.

   [IANA.senml]
              IANA, "Sensor Measurement Lists (SenML)",
              <https://www.iana.org/assignments/senml>.

   [RFC0020]  Cerf, V., "ASCII format for network interchange", STD 80,
              RFC 20, DOI 10.17487/RFC0020, October 1969,
              <https://www.rfc-editor.org/info/rfc20>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <https://www.rfc-editor.org/info/rfc4122>.

   [RFC6901]  Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
              "JavaScript Object Notation (JSON) Pointer", RFC 6901,
              DOI 10.17487/RFC6901, April 2013,
              <https://www.rfc-editor.org/info/rfc6901>.

   [RFC7396]  Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396,
              DOI 10.17487/RFC7396, October 2014,
              <https://www.rfc-editor.org/info/rfc7396>.






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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8428]  Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
              DOI 10.17487/RFC8428, August 2018,
              <https://www.rfc-editor.org/info/rfc8428>.

   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/info/rfc8610>.

   [RFC8798]  Bormann, C., "Additional Units for Sensor Measurement
              Lists (SenML)", RFC 8798, DOI 10.17487/RFC8798, June 2020,
              <https://www.rfc-editor.org/info/rfc8798>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/info/rfc8949>.

   [SPDX]     "SPDX License List", <https://spdx.org/licenses/>.

   [W3C.NOTE-curie-20101216]
              Birbeck, M. and S. McCarron, "CURIE Syntax 1.0", World
              Wide Web Consortium NOTE NOTE-curie-20101216, 16 December
              2010, <https://www.w3.org/TR/2010/NOTE-curie-20101216>.

9.2.  Informative References

   [ECMA-262] Ecma International, "ECMAScript 2020 Language
              Specification", ECMA Standard ECMA-262, 11th Edition, June
              2020, <https://www.ecma-international.org/wp-
              content/uploads/ECMA-262.pdf>.

   [I-D.bormann-jsonpath-iregexp]
              Bormann, C., "I-Regexp: An Interoperable Regexp Format",
              Work in Progress, Internet-Draft, draft-bormann-jsonpath-
              iregexp-00, 12 May 2021, <https://www.ietf.org/archive/id/
              draft-bormann-jsonpath-iregexp-00.txt>.

   [I-D.handrews-json-schema-validation]
              Wright, A., Andrews, H., and B. Hutton, "JSON Schema
              Validation: A Vocabulary for Structural Validation of
              JSON", Work in Progress, Internet-Draft, draft-handrews-



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              json-schema-validation-02, 17 September 2019,
              <https://www.ietf.org/archive/id/draft-handrews-json-
              schema-validation-02.txt>.

   [I-D.irtf-t2trg-rest-iot]
              Keranen, A., Kovatsch, M., and K. Hartke, "Guidance on
              RESTful Design for Internet of Things Systems", Work in
              Progress, Internet-Draft, draft-irtf-t2trg-rest-iot-08, 25
              August 2021, <https://www.ietf.org/archive/id/draft-irtf-
              t2trg-rest-iot-08.txt>.

   [I-D.wright-json-schema]
              Wright, A. and H. Andrews, "JSON Schema: A Media Type for
              Describing JSON Documents", Work in Progress, Internet-
              Draft, draft-wright-json-schema-01, 16 April 2017,
              <https://www.ietf.org/archive/id/draft-wright-json-schema-
              01.txt>.

   [OCF]      "OCF Resource Type Specification",
              <https://openconnectivity.org/specs/
              OCF_Resource_Type_Specification.pdf>.

   [OMA]      "OMA LightweightM2M (LwM2M) Object and Resource Registry",
              <http://www.openmobilealliance.org/wp/omna/lwm2m/
              lwm2mregistry.html>.

   [RFC8576]  Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of
              Things (IoT) Security: State of the Art and Challenges",
              RFC 8576, DOI 10.17487/RFC8576, April 2019,
              <https://www.rfc-editor.org/info/rfc8576>.

   [ZCL]      "The ZigBee Cluster Library", Zigbee Wireless
              Networking pp. 239-271,
              DOI 10.1016/b978-0-7506-8597-9.00006-9, 2008,
              <https://doi.org/10.1016/b978-0-7506-8597-9.00006-9>.

Appendix A.  Formal Syntax of SDF

   This appendix describes the syntax of SDF using CDDL [RFC8610].  Note
   that this appendix was derived from Ari Keranen's "alt-schema" and
   Michael Koster's "schema", with a view of covering the syntax that is
   currently in use at the One Data Model playground repository.









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   This appendix shows the framework syntax only, i.e., a syntax with
   liberal extension points.  Since this syntax is nearly useless in
   finding typos in an SDF specification, a second syntax, the
   validation syntax, is defined that does not include the extension
   points.  The validation syntax can be generated from the framework
   syntax by leaving out all lines containing the string EXTENSION-
   POINT; as this is trivial, the result is not shown here.

   This appendix makes use of CDDL "features" as defined in Section 4 of
   [I-D.ietf-cbor-cddl-control].  A feature named "1.0" is used to
   indicate parts of the syntax being deprecated towards SDF 1.1, and a
   feature named "1.1" is used to indicate new syntax intended for SDF
   1.1.  Features whose names end in "-ext" indicate extension points
   for further evolution.

   start = sdf-syntax

   sdf-syntax = {
    ? info: sdfinfo                  ; This will be required in most process policies, but not a syntax error
    ? namespace: named<text>
    ? defaultNamespace: text
    ? sdfThing: named<thingqualities>       ; Thing is a composition of objects that work together in some way
    ? sdfProduct: named<productqualities>   ; Product is a composition of things and objects that can model a SKU-level instance of a product
    ? sdfObject: named<objectqualities>     ; Object is a set of Properties, Actions, and Events that together perform a particular function
    ? sdfProperty: named<propertyqualities> ; Property represents the state of an instance of an object
    ? sdfAction: named<actionqualities>     ; Action is a directive to invoke an application layer verb associated with an object
    ? sdfEvent: named<eventqualities>       ; Event represents an occurrence of something associated with an object
    ? sdfData: named<dataqualities>         ; Data represents a piece of information that can be the state of a property or a parameter to an action or a signal in an event
    EXTENSION-POINT<"top-ext">
   }

   sdfinfo = {
    title: text
    version: text
    copyright: text
    license: text
    EXTENSION-POINT<"info-ext">
   }

   ; Shortcut for a map that gives names to instances of X (has text keys and values of type X)
   named<X> = { * text => X }

   EXTENSION-POINT<f> = ( * (text .feature f) => any ) ; only used in framework syntax

   sdf-pointer = text ; .regexp curie-regexp -- TO DO!
   pointer-list = [* sdf-pointer]  ; ISSUE: no point in having an empty list, no? but used for sdfRequired in odmobject-multiple_axis_joystick.sdf.json

   commonqualities = (



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    ? description: text            ; long text (no constraints)
    ? label: text                  ; short text (no constraints); default to key
    ? $comment: text               ; source code comments only, no semantics
    ? sdfRef: sdf-pointer
    ? sdfRequired: pointer-list    ; applies to qualities of properties, of data
   )

   ; for building hierarchy
   thingqualities = {
    commonqualities,
    ? sdfObject: named<objectqualities>
    ? sdfThing: named<thingqualities>
    EXTENSION-POINT<"thing-ext">
   }

   productqualities = thingqualities ; ISSUE: get rid of sdfProduct?

   ; for single objects, or for arrays of objects (1.2)
   objectqualities = {
    commonqualities,
    ? ("minItems" .feature "1.2") => number
    ? ("maxItems" .feature "1.2") => number
    ? sdfProperty: named<propertyqualities>
    ? sdfAction: named<actionqualities>
    ? sdfEvent: named<eventqualities>
    ? sdfData: named<dataqualities>
    EXTENSION-POINT<"object-ext">
   }

   propertyqualities = dataqualities ; the definitions in sdfData are declarations in sdfProperty

   parameter-list =
     pointer-list .feature (["1.0", "pointerlist-as-parameter"]) /
     dataqualities .feature (["1.1", "dataqualities-as-parameter"])

   actionqualities = {
    commonqualities,
    ? sdfInputData: parameter-list   ; sdfRequiredInputData applies here (a bit redundant)
    ? ("sdfRequiredInputData" .feature "1.0") => pointer-list
    ? sdfOutputData: parameter-list  ; sdfRequired applies here
    ? sdfData: named<dataqualities>         ; zero or more named data type definitions that might be used in the above
    EXTENSION-POINT<"action-ext">
   }

   eventqualities = {
    commonqualities
    ? sdfOutputData: parameter-list  ; sdfRequired applies here
    ? sdfData: named<dataqualities>         ; zero or more named data type definitions that might be used in the above



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    EXTENSION-POINT<"event-ext">
   }

   dataqualities = {               ; also propertyqualities
    commonqualities,
    jsonschema,
    ? ("units" .feature "1.0") => text
    ? ("unit" .feature "1.1") => text
    ? ("scaleMinimum" .feature "1.0") => number
    ? ("scaleMaximum" .feature "1.0") => number
    ? observable: bool
    ? readable: bool
    ? writable: bool
    ? nullable: bool
    ? ("subtype" .feature "1.0") => "byte-string" / "unix-time"
               / (text .feature "subtype-ext")                       ; EXTENSION-POINT
    ? ("sdfType" .feature "1.1") => "byte-string" / "unix-time"
               / (text .feature "sdftype-ext")                       ; EXTENSION-POINT
    ? contentFormat: text
    EXTENSION-POINT<"data-ext">
   }

   allowed-types = number / text / bool / null
                 / [* number] / [* text] / [* bool]
                 / {* text => any}
                 / (any .feature "allowed-ext")                     ; EXTENSION-POINT

   compound-type = (
     "type" => ("object" .feature "1.1"),
     ? required: [+text],
     ? properties: named<dataqualities>,
   )

   choice-type = (
     ("sdfChoice" .feature "1.1") => named<dataqualities>
   )

   jsonschema = (
    ? (("type" => "number" / "string" / "boolean" / "integer" / "array")
       // compound-type
       // choice-type
       // (type: text .feature "type-ext")                       ; EXTENSION-POINT
      )
    ? "enum" => [+ text]               ; limited to text strings in SDF 1.1
    ? ("enum" .feature "1.0") => [+ allowed-types]    ; should validate against type
    ? const: allowed-types                            ; should validate against type
    ? default: allowed-types                          ; should validate against type
    ; number/integer constraints



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    ? minimum: number
    ? maximum: number
    ? exclusiveMinimum: bool / number      ; jso draft 4/7
    ? exclusiveMaximum: bool / number      ; jso draft 4/7
    ? multipleOf: number                   ; ISSUE: Do we need this?
    ; text string constraints
    ? minLength: number
    ? maxLength: number
    ? pattern: text                ; regexp
    ? format: "date-time" / "date" / "time"
              / "uri" / "uri-reference" / "uuid"
              / (text .feature "format-ext")                       ; EXTENSION-POINT
    ; array constraints
    ? minItems: number
    ? maxItems: number
    ? uniqueItems: bool
    ? items: { ;;; ultimately, this will be mostly recursive, but, for now
               ;;; let's find out what we actually need
        ? sdfRef: sdf-pointer          ; import limited to the subset that we allow here...
        ? description: text            ; long text (no constraints)
        ? $comment: text               ; source code comments only, no semantics
        ; commonqualities, ; -- ISSUE: should leave this out for non-complex data types, but need the above three
        ? ((type: "number" / "string" / "boolean" / "integer") ; no "array"
           // compound-type
           // choice-type              ; do we really need arrays of choices?
           // (type: text .feature "itemtype-ext")                       ; EXTENSION-POINT
          )
        ; jso subset
        ? minimum: number
        ? maximum: number
        ? "enum" => [+ text] ; limited to text strings in SDF 1.1
        ? ("enum" .feature "1.0") => [+ any]
        ? format: text
        ? minLength: number
        ? maxLength: number
        EXTENSION-POINT<"items-ext">
      }
   )

Appendix B.  json-schema.org Rendition of SDF Syntax

   This appendix describes the syntax of SDF defined in Appendix A, but
   using a version of the description techniques advertised on json-
   schema.org [I-D.handrews-json-schema-validation].







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   The appendix shows both the validation and the framework syntax.
   Since most of the lines are the same between these two files, those
   lines are shown only once, with a leading space, in the form of a
   unified diff.  Lines leading with a - are part of the validation
   syntax, and lines leading with a + are part of the framework syntax.

    {
   -  "title": "sdf-validation.cddl",
   +  "title": "sdf-framework.cddl",
      "$schema": "http://json-schema.org/draft-07/schema#",
      "$ref": "#/definitions/sdf-syntax",
      "definitions": {
        "sdf-syntax": {
          "type": "object",
          "properties": {
            "info": {
              "$ref": "#/definitions/sdfinfo"
            },
            "namespace": {
              "type": "object",
              "additionalProperties": {
                "type": "string"
              }
            },
            "defaultNamespace": {
              "type": "string"
            },
            "sdfThing": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/thingqualities"
              }
            },
            "sdfProduct": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/productqualities"
              }
            },
            "sdfObject": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/objectqualities"
              }
            },
            "sdfProperty": {
              "type": "object",
              "additionalProperties": {



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                "$ref": "#/definitions/propertyqualities"
              }
            },
            "sdfAction": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/actionqualities"
              }
            },
            "sdfEvent": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/eventqualities"
              }
            },
            "sdfData": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/dataqualities"
              }
            }
          },
   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "sdfinfo": {
          "type": "object",
          "required": [
            "title",
            "version",
            "copyright",
            "license"
          ],
          "properties": {
            "title": {
              "type": "string"
            },
            "version": {
              "type": "string"
            },
            "copyright": {
              "type": "string"
            },
            "license": {
              "type": "string"
            }
          },



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   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "thingqualities": {
          "type": "object",
          "properties": {
            "description": {
              "type": "string"
            },
            "label": {
              "type": "string"
            },
            "$comment": {
              "type": "string"
            },
            "sdfRef": {
              "$ref": "#/definitions/sdf-pointer"
            },
            "sdfRequired": {
              "$ref": "#/definitions/pointer-list"
            },
            "sdfObject": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/objectqualities"
              }
            },
            "sdfThing": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/thingqualities"
              }
            }
          },
   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "sdf-pointer": {
          "type": "string"
        },
        "pointer-list": {
          "type": "array",
          "items": {
            "$ref": "#/definitions/sdf-pointer"
          }
        },



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        "objectqualities": {
          "type": "object",
          "properties": {
            "description": {
              "type": "string"
            },
            "label": {
              "type": "string"
            },
            "$comment": {
              "type": "string"
            },
            "sdfRef": {
              "$ref": "#/definitions/sdf-pointer"
            },
            "sdfRequired": {
              "$ref": "#/definitions/pointer-list"
            },
            "minItems": {
              "type": "number"
            },
            "maxItems": {
              "type": "number"
            },
            "sdfProperty": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/propertyqualities"
              }
            },
            "sdfAction": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/actionqualities"
              }
            },
            "sdfEvent": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/eventqualities"
              }
            },
            "sdfData": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/dataqualities"
              }
            }



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          },
   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "propertyqualities": {
          "$ref": "#/definitions/dataqualities"
        },
        "dataqualities": {
          "anyOf": [
            {
              "type": "object",
              "properties": {
                "type": {
                  "type": "string",
                  "enum": [
                    "number",
                    "string",
                    "boolean",
                    "integer",
                    "array"
                  ]
                },
                "enum": {
                  "type": "array",
                  "items": {
   -                "type": "string"
   +                "$ref": "#/definitions/allowed-types"
                  },
                  "minItems": 1
                },
                "const": {
                  "$ref": "#/definitions/allowed-types"
                },
                "default": {
                  "$ref": "#/definitions/allowed-types"
                },
                "minimum": {
                  "type": "number"
                },
                "maximum": {
                  "type": "number"
                },
                "exclusiveMinimum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },



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                    {
                      "type": "number"
                    }
                  ]
                },
                "exclusiveMaximum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },
                    {
                      "type": "number"
                    }
                  ]
                },
                "multipleOf": {
                  "type": "number"
                },
                "minLength": {
                  "type": "number"
                },
                "maxLength": {
                  "type": "number"
                },
                "pattern": {
                  "type": "string"
                },
                "format": {
   -              "type": "string",
   -              "enum": [
   -                "date-time",
   -                "date",
   -                "time",
   -                "uri",
   -                "uri-reference",
   -                "uuid"
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "date-time"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "date"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "time"



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   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri-reference"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uuid"
   +                },
   +                {
   +                  "type": "string"
   +                }
                  ]
                },
                "minItems": {
                  "type": "number"
                },
                "maxItems": {
                  "type": "number"
                },
                "uniqueItems": {
                  "type": "boolean"
                },
                "items": {
                  "anyOf": [
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "enum": [
                            "number",
                            "string",
                            "boolean",
                            "integer"
                          ]
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {



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                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "const": "object"
                        },
                        "required": {
                          "type": "array",
                          "items": {
                            "type": "string"
                          },
                          "minItems": 1
                        },
                        "properties": {
                          "type": "object",
                          "additionalProperties": {
                            "$ref": "#/definitions/dataqualities"
                          }



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                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {
                        "sdfChoice": {
                          "type": "object",
                          "additionalProperties": {
                            "$ref": "#/definitions/dataqualities"
                          }
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"



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                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string"
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"



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   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
                    }
                  ]
                },
                "description": {
                  "type": "string"
                },
                "label": {
                  "type": "string"
                },
                "$comment": {
                  "type": "string"
                },
                "sdfRef": {
                  "$ref": "#/definitions/sdf-pointer"
                },
                "sdfRequired": {
                  "$ref": "#/definitions/pointer-list"
                },
   +            "units": {
   +              "type": "string"
   +            },
                "unit": {
                  "type": "string"
                },
   +            "scaleMinimum": {



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   +              "type": "number"
   +            },
   +            "scaleMaximum": {
   +              "type": "number"
   +            },
                "observable": {
                  "type": "boolean"
                },
                "readable": {
                  "type": "boolean"
                },
                "writable": {
                  "type": "boolean"
                },
                "nullable": {
                  "type": "boolean"
                },
   +            "subtype": {
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
                "sdfType": {
   -              "type": "string",
   -              "enum": [
   -                "byte-string",
   -                "unix-time"
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"



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   +                }
                  ]
                },
                "contentFormat": {
                  "type": "string"
                }
              },
   -          "additionalProperties": false
   +          "additionalProperties": {
   +          }
            },
            {
              "type": "object",
              "properties": {
                "type": {
                  "type": "string",
                  "const": "object"
                },
                "required": {
                  "type": "array",
                  "items": {
                    "type": "string"
                  },
                  "minItems": 1
                },
                "properties": {
                  "type": "object",
                  "additionalProperties": {
                    "$ref": "#/definitions/dataqualities"
                  }
                },
                "enum": {
                  "type": "array",
                  "items": {
   -                "type": "string"
   +                "$ref": "#/definitions/allowed-types"
                  },
                  "minItems": 1
                },
                "const": {
                  "$ref": "#/definitions/allowed-types"
                },
                "default": {
                  "$ref": "#/definitions/allowed-types"
                },
                "minimum": {
                  "type": "number"
                },



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                "maximum": {
                  "type": "number"
                },
                "exclusiveMinimum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },
                    {
                      "type": "number"
                    }
                  ]
                },
                "exclusiveMaximum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },
                    {
                      "type": "number"
                    }
                  ]
                },
                "multipleOf": {
                  "type": "number"
                },
                "minLength": {
                  "type": "number"
                },
                "maxLength": {
                  "type": "number"
                },
                "pattern": {
                  "type": "string"
                },
                "format": {
   -              "type": "string",
   -              "enum": [
   -                "date-time",
   -                "date",
   -                "time",
   -                "uri",
   -                "uri-reference",
   -                "uuid"
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "date-time"



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   +                },
   +                {
   +                  "type": "string",
   +                  "const": "date"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "time"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri-reference"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uuid"
   +                },
   +                {
   +                  "type": "string"
   +                }
                  ]
                },
                "minItems": {
                  "type": "number"
                },
                "maxItems": {
                  "type": "number"
                },
                "uniqueItems": {
                  "type": "boolean"
                },
                "items": {
                  "anyOf": [
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "enum": [
                            "number",
                            "string",
                            "boolean",
                            "integer"
                          ]



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                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "const": "object"
                        },
                        "required": {
                          "type": "array",
                          "items": {
                            "type": "string"



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                          },
                          "minItems": 1
                        },
                        "properties": {
                          "type": "object",
                          "additionalProperties": {
                            "$ref": "#/definitions/dataqualities"
                          }
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {



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                        "sdfChoice": {
                          "type": "object",
                          "additionalProperties": {
                            "$ref": "#/definitions/dataqualities"
                          }
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string"
   +                    },



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   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
                    }
                  ]
                },
                "description": {
                  "type": "string"
                },
                "label": {
                  "type": "string"
                },
                "$comment": {
                  "type": "string"
                },
                "sdfRef": {
                  "$ref": "#/definitions/sdf-pointer"
                },
                "sdfRequired": {
                  "$ref": "#/definitions/pointer-list"



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                },
   +            "units": {
   +              "type": "string"
   +            },
                "unit": {
                  "type": "string"
                },
   +            "scaleMinimum": {
   +              "type": "number"
   +            },
   +            "scaleMaximum": {
   +              "type": "number"
   +            },
                "observable": {
                  "type": "boolean"
                },
                "readable": {
                  "type": "boolean"
                },
                "writable": {
                  "type": "boolean"
                },
                "nullable": {
                  "type": "boolean"
                },
   +            "subtype": {
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
                "sdfType": {
   -              "type": "string",
   -              "enum": [
   -                "byte-string",
   -                "unix-time"
   +              "anyOf": [
   +                {
   +                  "type": "string",



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   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
                  ]
                },
                "contentFormat": {
                  "type": "string"
                }
              },
   -          "additionalProperties": false
   +          "additionalProperties": {
   +          }
            },
            {
              "type": "object",
              "properties": {
                "sdfChoice": {
                  "type": "object",
                  "additionalProperties": {
                    "$ref": "#/definitions/dataqualities"
                  }
                },
                "enum": {
                  "type": "array",
                  "items": {
   -                "type": "string"
   +                "$ref": "#/definitions/allowed-types"
                  },
                  "minItems": 1
                },
                "const": {
                  "$ref": "#/definitions/allowed-types"
                },
                "default": {
                  "$ref": "#/definitions/allowed-types"
                },
                "minimum": {
                  "type": "number"
                },
                "maximum": {
                  "type": "number"
                },



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                "exclusiveMinimum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },
                    {
                      "type": "number"
                    }
                  ]
                },
                "exclusiveMaximum": {
                  "anyOf": [
                    {
                      "type": "boolean"
                    },
                    {
                      "type": "number"
                    }
                  ]
                },
                "multipleOf": {
                  "type": "number"
                },
                "minLength": {
                  "type": "number"
                },
                "maxLength": {
                  "type": "number"
                },
                "pattern": {
                  "type": "string"
                },
                "format": {
   -              "type": "string",
   -              "enum": [
   -                "date-time",
   -                "date",
   -                "time",
   -                "uri",
   -                "uri-reference",
   -                "uuid"
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "date-time"
   +                },
   +                {
   +                  "type": "string",



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   +                  "const": "date"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "time"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri-reference"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uuid"
   +                },
   +                {
   +                  "type": "string"
   +                }
                  ]
                },
                "minItems": {
                  "type": "number"
                },
                "maxItems": {
                  "type": "number"
                },
                "uniqueItems": {
                  "type": "boolean"
                },
                "items": {
                  "anyOf": [
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "enum": [
                            "number",
                            "string",
                            "boolean",
                            "integer"
                          ]
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"



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                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {
                        "type": {
                          "type": "string",
                          "const": "object"
                        },
                        "required": {
                          "type": "array",
                          "items": {
                            "type": "string"
                          },
                          "minItems": 1
                        },



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                        "properties": {
                          "type": "object",
                          "additionalProperties": {
                            "$ref": "#/definitions/dataqualities"
                          }
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
                    },
                    {
                      "type": "object",
                      "properties": {
                        "sdfChoice": {
                          "type": "object",
                          "additionalProperties": {



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                            "$ref": "#/definitions/dataqualities"
                          }
                        },
                        "sdfRef": {
                          "$ref": "#/definitions/sdf-pointer"
                        },
                        "description": {
                          "type": "string"
                        },
                        "$comment": {
                          "type": "string"
                        },
                        "minimum": {
                          "type": "number"
                        },
                        "maximum": {
                          "type": "number"
                        },
                        "enum": {
                          "type": "array",
   -                      "items": {
   -                        "type": "string"
   -                      },
                          "minItems": 1
                        },
                        "format": {
                          "type": "string"
                        },
                        "minLength": {
                          "type": "number"
                        },
                        "maxLength": {
                          "type": "number"
                        }
                      },
   -                  "additionalProperties": false
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string"
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },



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   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
                    }
                  ]
                },
                "description": {
                  "type": "string"
                },
                "label": {
                  "type": "string"
                },
                "$comment": {
                  "type": "string"
                },
                "sdfRef": {
                  "$ref": "#/definitions/sdf-pointer"
                },
                "sdfRequired": {
                  "$ref": "#/definitions/pointer-list"
                },
   +            "units": {
   +              "type": "string"



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   +            },
                "unit": {
                  "type": "string"
                },
   +            "scaleMinimum": {
   +              "type": "number"
   +            },
   +            "scaleMaximum": {
   +              "type": "number"
   +            },
                "observable": {
                  "type": "boolean"
                },
                "readable": {
                  "type": "boolean"
                },
                "writable": {
                  "type": "boolean"
                },
                "nullable": {
                  "type": "boolean"
                },
   -            "sdfType": {
   -              "type": "string",
   -              "enum": [
   -                "byte-string",
   -                "unix-time"
   -              ]
   -            },
   +            "subtype": {
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
   +            "sdfType": {
   +              "anyOf": [
   +                {
   +                  "type": "string",



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   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
                "contentFormat": {
                  "type": "string"
                }
              },
   -          "additionalProperties": false
   +          "additionalProperties": {
   +          }
   +        },
   +        {
   +          "type": "object",
   +          "properties": {
   +            "type": {
   +              "type": "string"
   +            },
   +            "enum": {
   +              "type": "array",
   +              "items": {
   +                "$ref": "#/definitions/allowed-types"
   +              },
   +              "minItems": 1
   +            },
   +            "const": {
   +              "$ref": "#/definitions/allowed-types"
   +            },
   +            "default": {
   +              "$ref": "#/definitions/allowed-types"
   +            },
   +            "minimum": {
   +              "type": "number"
   +            },
   +            "maximum": {
   +              "type": "number"
   +            },
   +            "exclusiveMinimum": {
   +              "anyOf": [
   +                {
   +                  "type": "boolean"



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   +                },
   +                {
   +                  "type": "number"
   +                }
   +              ]
   +            },
   +            "exclusiveMaximum": {
   +              "anyOf": [
   +                {
   +                  "type": "boolean"
   +                },
   +                {
   +                  "type": "number"
   +                }
   +              ]
   +            },
   +            "multipleOf": {
   +              "type": "number"
   +            },
   +            "minLength": {
   +              "type": "number"
   +            },
   +            "maxLength": {
   +              "type": "number"
   +            },
   +            "pattern": {
   +              "type": "string"
   +            },
   +            "format": {
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "date-time"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "date"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "time"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uri"
   +                },
   +                {
   +                  "type": "string",



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   +                  "const": "uri-reference"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "uuid"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
   +            "minItems": {
   +              "type": "number"
   +            },
   +            "maxItems": {
   +              "type": "number"
   +            },
   +            "uniqueItems": {
   +              "type": "boolean"
   +            },
   +            "items": {
   +              "anyOf": [
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string",
   +                      "enum": [
   +                        "number",
   +                        "string",
   +                        "boolean",
   +                        "integer"
   +                      ]
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"



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   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string",
   +                      "const": "object"
   +                    },
   +                    "required": {
   +                      "type": "array",
   +                      "items": {
   +                        "type": "string"
   +                      },
   +                      "minItems": 1
   +                    },
   +                    "properties": {
   +                      "type": "object",
   +                      "additionalProperties": {
   +                        "$ref": "#/definitions/dataqualities"
   +                      }
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {



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   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "sdfChoice": {
   +                      "type": "object",
   +                      "additionalProperties": {
   +                        "$ref": "#/definitions/dataqualities"
   +                      }
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",



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   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"
   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
   +                },
   +                {
   +                  "type": "object",
   +                  "properties": {
   +                    "type": {
   +                      "type": "string"
   +                    },
   +                    "sdfRef": {
   +                      "$ref": "#/definitions/sdf-pointer"
   +                    },
   +                    "description": {
   +                      "type": "string"
   +                    },
   +                    "$comment": {
   +                      "type": "string"
   +                    },
   +                    "minimum": {
   +                      "type": "number"
   +                    },
   +                    "maximum": {
   +                      "type": "number"
   +                    },
   +                    "enum": {
   +                      "type": "array",
   +                      "minItems": 1
   +                    },
   +                    "format": {
   +                      "type": "string"
   +                    },
   +                    "minLength": {
   +                      "type": "number"
   +                    },
   +                    "maxLength": {
   +                      "type": "number"



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   +                    }
   +                  },
   +                  "additionalProperties": {
   +                  }
   +                }
   +              ]
   +            },
   +            "description": {
   +              "type": "string"
   +            },
   +            "label": {
   +              "type": "string"
   +            },
   +            "$comment": {
   +              "type": "string"
   +            },
   +            "sdfRef": {
   +              "$ref": "#/definitions/sdf-pointer"
   +            },
   +            "sdfRequired": {
   +              "$ref": "#/definitions/pointer-list"
   +            },
   +            "units": {
   +              "type": "string"
   +            },
   +            "unit": {
   +              "type": "string"
   +            },
   +            "scaleMinimum": {
   +              "type": "number"
   +            },
   +            "scaleMaximum": {
   +              "type": "number"
   +            },
   +            "observable": {
   +              "type": "boolean"
   +            },
   +            "readable": {
   +              "type": "boolean"
   +            },
   +            "writable": {
   +              "type": "boolean"
   +            },
   +            "nullable": {
   +              "type": "boolean"
   +            },
   +            "subtype": {
   +              "anyOf": [



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   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
   +            "sdfType": {
   +              "anyOf": [
   +                {
   +                  "type": "string",
   +                  "const": "byte-string"
   +                },
   +                {
   +                  "type": "string",
   +                  "const": "unix-time"
   +                },
   +                {
   +                  "type": "string"
   +                }
   +              ]
   +            },
   +            "contentFormat": {
   +              "type": "string"
   +            }
   +          },
   +          "additionalProperties": {
   +          }
            }
          ]
        },
        "allowed-types": {
          "anyOf": [
            {
              "type": "number"
            },
            {
              "type": "string"
            },
            {
              "type": "boolean"
            },



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            {
              "type": "null"
            },
            {
              "type": "array",
              "items": {
                "type": "number"
              }
            },
            {
              "type": "array",
              "items": {
                "type": "string"
              }
            },
            {
              "type": "array",
              "items": {
                "type": "boolean"
              }
            },
            {
              "type": "object",
              "additionalProperties": {
              }
   +        },
   +        {
            }
          ]
        },
        "actionqualities": {
          "type": "object",
          "properties": {
            "description": {
              "type": "string"
            },
            "label": {
              "type": "string"
            },
            "$comment": {
              "type": "string"
            },
            "sdfRef": {
              "$ref": "#/definitions/sdf-pointer"
            },
            "sdfRequired": {
              "$ref": "#/definitions/pointer-list"
            },



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            "sdfInputData": {
              "$ref": "#/definitions/parameter-list"
            },
   +        "sdfRequiredInputData": {
   +          "$ref": "#/definitions/pointer-list"
   +        },
            "sdfOutputData": {
              "$ref": "#/definitions/parameter-list"
            },
            "sdfData": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/dataqualities"
              }
            }
          },
   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "parameter-list": {
   -      "$ref": "#/definitions/dataqualities"
   +      "anyOf": [
   +        {
   +          "$ref": "#/definitions/pointer-list"
   +        },
   +        {
   +          "$ref": "#/definitions/dataqualities"
   +        }
   +      ]
        },
        "eventqualities": {
          "type": "object",
          "properties": {
            "description": {
              "type": "string"
            },
            "label": {
              "type": "string"
            },
            "$comment": {
              "type": "string"
            },
            "sdfRef": {
              "$ref": "#/definitions/sdf-pointer"
            },
            "sdfRequired": {
              "$ref": "#/definitions/pointer-list"



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            },
            "sdfOutputData": {
              "$ref": "#/definitions/parameter-list"
            },
            "sdfData": {
              "type": "object",
              "additionalProperties": {
                "$ref": "#/definitions/dataqualities"
              }
            }
          },
   -      "additionalProperties": false
   +      "additionalProperties": {
   +      }
        },
        "productqualities": {
          "$ref": "#/definitions/thingqualities"
        }
      }
    }

Appendix C.  Data Qualities inspired by json-schema.org

   Data qualities define data used in SDF affordances at an information
   model level.  A popular way to describe JSON data at a data model
   level is proposed by a number of drafts on json-schema.org (which
   collectively are abbreviated JSO here)); for reference to a popular
   version we will point here to [I-D.handrews-json-schema-validation].
   As the vocabulary used by JSO is familiar to many JSON modellers, the
   present specification borrows some of the terms and ports their
   semantics to the information model level needed for SDF.

   The main data quality imported is the "type".  In SDF, this can take
   one of six (text string) values, which are discussed in the following
   subsections (note that the JSO type "null" is not supported as a
   value of this data quality in SDF).

   The additional quality "const" restricts the data to one specific
   value (given as the value of the const quality).

   Similarly, the additional quality "default" provides data that can be
   used in the absence of the data (given as the value of the const
   quality); this is mainly documentary and not very well-defined for
   SDF as no process is defined that would add default values to an
   instance of something.






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C.1.  type "number", type "integer"

   The types "number" and "integer" are associated with floating point
   and integer numbers, as they are available in JSON.  A type value of
   integer means that only integer values of JSON numbers can be used
   (note that 10.0 is an integer value, even if it is in a notation that
   would also allow non-zero decimal fractions).

   The additional data qualities "minimum", "maximum",
   "exclusiveMinimum", "exclusiveMaximum" provide number values that
   serve as inclusive/exclusive lower/upper bounds for the number.
   (Note that the Boolean form of "exclusiveMinimum"/"exclusiveMaximum"
   found in earlier JSO drafts is not used.)

   The data quality "multipleOf" gives a positive number that constrains
   the data value to be an integer multiple of the number given.  (Type
   "integer" can also be expressed as a "multipleOf" quality of value 1,
   unless another "multipleOf" quality is present.)

C.2.  type "string"

   The type "string" is associated with Unicode text string values as
   they are available in JSON.

   The length (as measured in characters) can be constrained by the
   additional data qualities "minLength" and "maxLength", which are
   inclusive bounds.  Note that the previous version of the present
   document explained text string length values in bytes, which however
   is not meaningful unless bound to a specific encoding (which could be
   UTF-8, if this unusual behavior is to be restored).

   The data quality "pattern" takes a string value that is interpreted
   as an [ECMA-262] regular expression in Unicode mode that constrain
   the string (note that these are not anchored by default, so unless ^
   and $ anchors are employed, ECMA-262 regular expressions match any
   string that _contains_ a match).  The JSO proposals acknowledge that
   regular expression support is rather diverse in various platforms, so
   the suggestion is to limit them to:

   *  characters;
   *  character classes in square brackets, including ranges; their
      complements;
   *  simple quantifiers *, +, ?, and range quantifiers {n}, {n,m}, and
      {n,};
   *  grouping parentheses;
   *  the choice operator |;
   *  and anchors (beginning-of-input ^ and end-of-input $).




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   Note that this subset is somewhat similar to the subset introduced by
   iregexps [I-D.bormann-jsonpath-iregexp], which however are anchored
   regular expressions, and which include certain backslash escapes for
   characters and character classes.

   The additional data quality "format" can take one of the following
   values.  Note that, at an information model level, the presence of
   this data quality changes the type from being a simple text string to
   the abstract meaning of the format given (i.e., the format "date-
   time" is less about the specific syntax employed in [RFC3339] than
   about the usage as an absolute point in civil time).

   *  "date-time", "date", "time": An [RFC3339] date-time, full-date, or
      full-time, respectively.
   *  "uri", "uri-reference": An [RFC3986] URI or URI Reference,
      respectively.
   *  "uuid": An [RFC4122] UUID.

C.3.  type "boolean"

   The type "boolean" can take the values "true" or "false".

C.4.  type "array"

   The type "array" is associated with arrays as they are available in
   JSON.

   The additional quality "items" gives the type that each of the
   elements of the array must match.

   The number of elements in the array can be constrained by the
   additional data qualities "minItems" and "maxItems", which are
   inclusive bounds.

   The additional data quality "uniqueItems" gives a Boolean value that,
   if true, requires the elements to be all different.

C.5.  type "object"

   The type "object" is associated with maps, from strings to values, as
   they are available in JSON ("objects").

   The additional quality "properties" is a map the entries of which
   describe entries in the specified JSON object: The key gives an
   allowable map key for the specified JSON object, and the value is a
   map with a named set of data qualities giving the type for the
   corresponding value in the specified JSON object.




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   All entries specified this way are optional, unless they are listed
   in the value of the additional quality "required", which is an array
   of string values that give the key names of required entries.

   Note that the term "properties" as an additional quality for defining
   map entries is unrelated to sdfProperty.

C.6.  Implementation notes

   JSO-based keywords are also used in the specification techniques of a
   number of ecosystems, but some adjustments may be required.

   E.g., [OCF] is based on Swagger 2.0 which appears to be based on
   "draft-4" [I-D.wright-json-schema] (also called draft-5, but
   semantically intended to be equivalent to draft-4).  The
   "exclusiveMinimum" and "exclusiveMaximum" keywords use the Boolean
   form there, so on import to SDF their values have to be replaced by
   the values of the respective "minimum"/"maximum" keyword, which are
   themselves then removed; the reverse transformation applies on
   export.

   TBD: add any useful implementation notes we can find for other
   ecosystems that use JSO.

Acknowledgements

   This draft is based on sdf.md and sdf-schema.json in the old one-
   data-model language repository, as well as Ari Keränen's "alt-schema"
   from the Ericsson Research ipso-odm repository (which is now under
   subdirectory sdflint in the one-data model tools repository).

Contributors

   Ari Keränen
   Ericsson
   FI-02420 Jorvas
   Finland

   Email: ari.keranen@ericsson.com


   Wouter van der Beek
   Cascoda Ltd.
   Threefield House
   Threefield Lane
   Southampton
   United Kingdom




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   Email: w.vanderbeek@cascoda.com


Authors' Addresses

   Michael Koster (editor)
   PassiveLogic
   524 H Street
   Antioch, CA,  94509
   United States of America

   Phone: +1-707-502-5136
   Email: michaeljohnkoster@gmail.com


   Carsten Bormann (editor)
   Universität Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany

   Phone: +49-421-218-63921
   Email: cabo@tzi.org




























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