DTNMA Application Resource Identifier (ARI)
draft-ietf-dtn-ari-02
| Document | Type | Active Internet-Draft (dtn WG) | |
|---|---|---|---|
| Authors | Edward J. Birrane , Emery Annis , Brian Sipos | ||
| Last updated | 2024-07-21 | ||
| Replaces | draft-birrane-dtn-ari | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
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| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-ietf-dtn-ari-02
Delay-Tolerant Networking E.J. Birrane
Internet-Draft E.A. Annis
Intended status: Standards Track B. Sipos
Expires: 22 January 2025 JHU/APL
21 July 2024
DTNMA Application Resource Identifier (ARI)
draft-ietf-dtn-ari-02
Abstract
This document defines the structure, format, and features of the
naming scheme for the objects defined in the Delay-Tolerant
Networking Management Architecture (DTNMA) Application Management
Model (AMM), in support of challenged network management solutions
described in the DTNMA document.
This document defines the DTNMA Application Resource Identifier
(ARI), using a text-form based on the common Uniform Resource
Identifier (URI) and a binary-form based on Concise Binary Object
Representation (CBOR). These meet the needs for a concise, typed,
parameterized, and hierarchically organized set of managed data
elements.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 22 January 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Use of ABNF . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Use of CDDL . . . . . . . . . . . . . . . . . . . . . . . 5
1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. ARI Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Resource Parameterization . . . . . . . . . . . . . . . . 6
2.2. Compressible Structure . . . . . . . . . . . . . . . . . 7
2.2.1. Enumerated Path Segments . . . . . . . . . . . . . . 7
2.2.2. Relative Paths . . . . . . . . . . . . . . . . . . . 8
2.2.3. Patterning . . . . . . . . . . . . . . . . . . . . . 8
3. ARI Logical Structure . . . . . . . . . . . . . . . . . . . . 8
3.1. Names, Enumerations, Comparisons, and
Canonicalizations . . . . . . . . . . . . . . . . . . . . 8
3.2. Literals . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Object References . . . . . . . . . . . . . . . . . . . . 11
3.3.1. Namespace ID . . . . . . . . . . . . . . . . . . . . 11
3.3.2. Object Type . . . . . . . . . . . . . . . . . . . . . 12
3.3.3. Object ID . . . . . . . . . . . . . . . . . . . . . . 12
3.3.4. Parameters . . . . . . . . . . . . . . . . . . . . . 12
3.4. Namespace References . . . . . . . . . . . . . . . . . . 14
4. ARI Text Form . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. URIs and Percent Encoding . . . . . . . . . . . . . . . . 15
4.2. Literals . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.1. Typed Literal Values . . . . . . . . . . . . . . . . 16
4.2.2. Untyped Literal Values . . . . . . . . . . . . . . . 21
4.2.3. Preferred Encodings . . . . . . . . . . . . . . . . . 22
4.3. Object References . . . . . . . . . . . . . . . . . . . . 23
4.4. Namespace References . . . . . . . . . . . . . . . . . . 24
4.5. ARI References . . . . . . . . . . . . . . . . . . . . . 25
5. ARI Binary Form . . . . . . . . . . . . . . . . . . . . . . . 25
5.1. Intermediate CBOR . . . . . . . . . . . . . . . . . . . . 25
5.2. Literals . . . . . . . . . . . . . . . . . . . . . . . . 26
5.3. Object References . . . . . . . . . . . . . . . . . . . . 28
5.3.1. Namespace References . . . . . . . . . . . . . . . . 30
5.3.2. ARI References . . . . . . . . . . . . . . . . . . . 30
6. Processing Activities . . . . . . . . . . . . . . . . . . . . 31
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6.1. ID Segment Translation . . . . . . . . . . . . . . . . . 31
6.2. ARI Reference Resolution . . . . . . . . . . . . . . . . 31
7. ARI Patterns . . . . . . . . . . . . . . . . . . . . . . . . 31
7.1. ARI Matching . . . . . . . . . . . . . . . . . . . . . . 32
8. Transcoding Considerations . . . . . . . . . . . . . . . . . 33
9. Interoperability Considerations . . . . . . . . . . . . . . . 33
10. Security Considerations . . . . . . . . . . . . . . . . . . . 34
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
11.1. URI Schemes Registry . . . . . . . . . . . . . . . . . . 34
11.2. DTN Management Architecture Parameters . . . . . . . . . 34
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
12.1. Normative References . . . . . . . . . . . . . . . . . . 40
12.2. Informative References . . . . . . . . . . . . . . . . . 42
Appendix A. Example Equivalences . . . . . . . . . . . . . . . . 43
A.1. Primitive-Typed Literal . . . . . . . . . . . . . . . . . 44
A.2. Timestamp Literal . . . . . . . . . . . . . . . . . . . . 45
A.3. Semantic-Typed Literal . . . . . . . . . . . . . . . . . 45
A.4. Complex CBOR Literal . . . . . . . . . . . . . . . . . . 45
A.5. Non-parameterized Object Reference . . . . . . . . . . . 46
A.6. Parameterized Object Reference . . . . . . . . . . . . . 46
A.7. Recursive Structure with Percent Encodings . . . . . . . 47
Appendix B. Implementation Guidance . . . . . . . . . . . . . . 47
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49
1. Introduction
The unique limitations of Delay-Tolerant Networking (DTN) transport
capabilities [RFC4838] necessitate increased reliance on individual
node behavior. These limitations are considered part of the expected
operational environment of the system and, thus, contemporaneous end-
to-end data exchange cannot be considered a requirement for
successful communication.
The primary DTN transport mechanism, Bundle Protocol version 7 (BPv7)
[RFC9171], standardizes a store-and-forward behavior required to
communicate effectively between endpoints that may never co-exist in
a single network partition. BPv7 might be deployed in static
environments, but the design and operation of BPv7 cannot presume
that to be the case.
Similarly, the management of any BPv7 protocol agent (BPA) (or any
software reliant upon DTN for its communication) cannot presume to
operate in a resourced, connected network. Just as DTN transport
must be delay-tolerant, DTN network management must also be delay-
tolerant.
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The DTN Management Architecture (DTNMA) [I-D.ietf-dtn-dtnma] outlines
an architecture that achieves this result through the self-management
of a DTN node as configured by one or more remote managers in an
asynchronous and open-loop system. An important part of this
architecture is the definition of a conceptual data schema for
defining resources configured by remote managers and implemented by
the local autonomy of a DTN node.
The DTNMA Application Management Model (AMM) [I-D.ietf-dtn-amm]
defines a logical schema that can be used to represent data types and
structures, autonomous controls, and other kinds of information
expected to be required for the local management of a DTN node. The
AMM further describes a physical data model, called the Application
Data Model (ADM), that can be defined in the context of applications
to create resources in accordance with the AMM schema. These named
resources can be predefined in moderated publications or custom-
defined as part of the Operational Data Model (ODM) of an agent.
Every AMM resource must be uniquely identifiable. To accomplish
this, an expressive naming scheme is required. The Application
Resource Identifier (ARI) provides this naming scheme. This document
defines the ARI, based on the structure of a Uniform Resource
Identifier (URI), meeting the needs for a concise, typed,
parameterized, and hierarchically organized naming convention.
1.1. Scope
The ARI scheme is based on the structure of a URI [RFC3986] in
accordance with the practices outlined in [RFC8820].
ARIs are designed to support the identification requirements of the
AMM logical schema. As such, this specification will discuss these
requirements to the extent necessary to explain the structure and use
of the ARI syntax.
This specification does not constrain the syntax or structure of any
existing URI (or part thereof). As such, the ARI scheme does not
impede the ownership of any other URI scheme and is therefore clear
of the concerns presented in [RFC7320].
This specification does not discuss the manner in which ARIs might be
generated, populated, and used by applications. The operational
utility and configuration of ARIs in a system are described in other
documents associated with DTN management, to include the DTNMA and
AMM specifications.
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This specification does not describe the way in which path prefixes
associated with an ARI are standardized, moderated, or otherwise
populated. Path suffixes may be specified where they do not lead to
collision or ambiguity.
This specification does not describe the mechanisms for generating
either standardized or custom ARIs in the context of any given
application, protocol, or network.
1.2. Use of ABNF
This document defines text structure using the Augmented Backus-Naur
Form (ABNF) of [RFC5234]. The entire ABNF structure can be extracted
from the XML version of this document using the XPath expression:
'//sourcecode[@type="abnf"]'
The following initial fragment defines the top-level rules of this
document's ABNF.
start = ari
From the document [RFC3986] the definitions are taken for pchar,
unreserved, pct-encoded. From the document [RFC3339] the definitions
are taken for date-time, full-date, and duration. From the document
[RFC5234] the definitions are taken for bit, hexdig, digit, and char-
val. From the document [RFC8259] the definitions are taken for char
and unescaped.
1.3. Use of CDDL
This document defines Concise Binary Object Representation (CBOR)
structure using the Concise Data Definition Language (CDDL) of
[RFC8610]. The entire CDDL structure can be extracted from the XML
version of this document using the XPath expression:
'//sourcecode[@type="cddl"]'
The following initial fragment defines the top-level symbols of this
document's CDDL, which includes the example CBOR content.
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start = ari
; Limited sizes to fit the AMM data model
int32 = (-2147483648 .. 2147483647) .within int
uint32 = uint .le 4294967295
int64 = (-9223372036854775808 .. 9223372036854775807) .within int
uint64 = uint
; Restricted identifier text
id-text = tstr .regexp "[A-Za-z_][A-Za-z0-9_-\.]*"
This document does not rely on any CDDL symbol names from other
documents.
1.4. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD 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.
The terms "Application Data Model", "Application Resource
Identifier", "Operational Data Model", "Externally Defined Data",
"Variable", "Constant", "Control", "Literal", "Macro", "Namespace",
"Operator", "Report", "Report Template", "Rule", "State-Based Rule",
"Table", and "Time-Based Rule" are used without modification from the
definitions provided in [I-D.ietf-dtn-amm].
2. ARI Purpose
ADM resources are referenced in the context of autonomous
applications on an agent. The naming scheme of these resources must
support certain features to inform DTNMA processing in accordance
with the ADM logical schema.
This section defines the set of unique characteristics of the ARI
scheme, the combination of which provides a unique utility for
naming. While certain other naming schemes might incorporate certain
elements, there are no such schemes that both support needed features
and exclude prohibited features.
2.1. Resource Parameterization
The ADM schema allows for the parameterization of resources to both
reduce the overall data volume communicated between DTN nodes and to
remove the need for any round-trip data negotiation.
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Parameterization reduces the communicated data volume when parameters
are used as filter criteria. By associating a parameter with a data
source, data characteristic, or other differentiating attribute, DTN
nodes can locally process parameters to construct the minimal set of
information to either process for local autonomy or report to remote
managers in the network.
Parameterization eliminates the need for round-trip negotiation to
identify where information is located or how it should be accessed.
When parameters define the ability to perform an associative lookup
of a value, the index or location of the data at a particular DTN
node can be resolved locally as part of the local autonomy of the
node and not communicated back to a remote manager.
2.2. Compressible Structure
The ability to encode information in very concise formats enables DTN
communications in a variety of ways. Reduced message sizes increase
the likelihood of message delivery, require fewer processing
resources to secure, store, and forward, and require less resources
to transmit.
While the encoding of an ARI is outside of the scope of this
document, the structure of portions of the ARI syntax lend themselves
to better compressibility. For example, DTN ADM encodings support
the ability to identify resources in as few as 3 bytes by exploiting
the compressible structure of the ARI.
The ARI syntax supports three design elements to aid in the creation
of more concise encodings: enumerated forms of path segments,
relative paths, and patterning.
2.2.1. Enumerated Path Segments
Because the ARI structure includes paths segments with stable
enumerated values, each segment can be represented by either its text
name or its integer enumeration. For human-readability in text form
the text name is preferred, but for binary encoding and for
comparisons the integer form is preferred. It is a translation done
by the entity handling an ARI to switch between preferred
representations (see Section 8); the data model of both forms of the
ARI allows for either.
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2.2.2. Relative Paths
Within an ARI, as defined in Section 3, literal values require no
external context to interpret an so have no use for relative paths.
Object reference values, however, always refer to an object within an
ADM or ODM namespace and this namespace can be used as a base for
resolving URI References as discussed in Section 4.5 and
Section 5.3.2.
2.2.3. Patterning
Patterning in this context refers to the structuring of ARI
information to allow for meaning data selection as a function of
wildcards, regular expressions, and other expressions of a pattern.
Patterns allow for both better compression and fewer ARI
representations by allowing a single ARI pattern to stand-in for a
variety of actual ARIs.
This benefit is best achieved when the structure of the ARI is both
expressive enough to include information that is useful to pattern
match, and regular enough to understand how to create these patterns.
3. ARI Logical Structure
This section describes the information model of the ARI scheme to
inform the discussion of the ARI syntax in Section 4 and Section 5.
At the top-level, an ARI represents one of of the following AMM value
classes defined in later subsections.
Literal values: These are values are those whose value and
identifier are equivalent and are discussed in more detail in
Section 3.2.
Object Reference values: These values refer to an individual object,
possibly with parameters, and are discussed in Section 3.3.
Namespace Reference values: These values refer to an individual
namespace and are discussed in Section 3.4.
3.1. Names, Enumerations, Comparisons, and Canonicalizations
Within the ARI logical model, there are a number of domains in which
items are identified by a combination of text name and integer
enumeration: ADMs, ODMs, literal types, object types, and objects.
In all cases, within a single domain the text name and integer
enumeration SHALL NOT be considered comparable. It is an explicit
activity by any entity processing ARIs to make the translation
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between text name and integer enumeration (see Section 8).
Text names SHALL be restricted to begin with an alphabetic character
followed by any number of other characters, as defined in the id-text
ABNF symbol. This excludes a large class of characters, including
non-printing characters. When represented in text form, the text
name for ODMs is prefixed with a "!" character to disambiguate it
from an ADM name (see Section 3.3).
For text names, comparison and uniqueness SHALL be based on case-
insensitive logic. The canonical form of text names SHALL be the
lower case representation.
Integer enumerations for ADMs and ODMs SHALL be restricted to a
magnitude less than 2**63 to allow them to fit within a signed 64-bit
storage. The ADM registration in Table 5 reserves high-valued code
points for private and experimental ADMs, while the entire domain of
ODM code points (negative integers) is considered private use.
Integer enumerations for literal types and object types SHALL be
restricted to a magnitude less than 2**31 to allow them to fit within
a signed 32-bit storage. The registrations in Table 2 and Table 3
respectively Integer enumerations for objects (within an ADM or ODM)
SHALL be restricted to a magnitude less than 2**31 to allow them to
fit within a signed 32-bit storage, although negative-value object
enumerations are disallowed.
For integer enumerations, comparison and uniqueness SHALL be based on
numeric values not on encoded forms. The canonical form of integer
enumerations in text form SHALL be the shortest length decimal
representation.
3.2. Literals
Literals represent a special class of ARI which are not associated
with any particular ADM or ODM. A literal has no other name other
than its value, but literals may be explicitly typed in order to
force the receiver to handle it in a specific way.
Because literals will be based on the CBOR data model [RFC8949] and
its extended diagnostic notation, a literal has an intrinsic
representable data type as well as an AMM data type. The CBOR
primitive types are named CDDL symbols as defined in Section 3.3 of
[RFC8610].
When converting from AMM literal types, the chosen CBOR type SHALL be
determined by the mapping in Table 1. Additionally, when handling
typed literal ARIs any combination of AMM literal type and CBOR
primitive type not in Table 1 SHALL be considered invalid. This
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restriction is enforced by the CDDL defined in Section 5.
Additionally, when handling a literal of AMM type CBOR the well-
formed-ness of the CBOR contained SHOULD be verified before the
literal is treated as valid.
+==================+================+
| AMM Literal Type | Used CBOR Type |
+==================+================+
| NULL | null |
+------------------+----------------+
| BOOL | bool |
+------------------+----------------+
| BYTE | uint |
+------------------+----------------+
| INT | int |
+------------------+----------------+
| UINT | uint |
+------------------+----------------+
| VAST | int |
+------------------+----------------+
| UVAST | uint |
+------------------+----------------+
| REAL32 | float |
+------------------+----------------+
| REAL64 | float |
+------------------+----------------+
| TEXTSTR | tstr |
+------------------+----------------+
| BYTESTR | bstr |
+==================+================+
| Non-primitive types |
+==================+================+
| TP | lit-time |
+------------------+----------------+
| TD | lit-time |
+------------------+----------------+
| LABEL | lit-label |
+------------------+----------------+
| CBOR | lit-cbor |
+==================+================+
| Containers |
+==================+================+
| AC | ari-collection |
+------------------+----------------+
| AM | ari-map |
+------------------+----------------+
| TBL | ari-tbl |
+------------------+----------------+
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| EXECSET | exec-set |
+------------------+----------------+
| RPTSET | rpt-set |
+------------------+----------------+
Table 1: AMM Literal Types to
CBOR Types
3.3. Object References
Object references are composed of two parts: object path and optional
parameters. The object path can be dereferenced to a specific object
in the ADM/ODM, while the parameters provide additional information
for certain types of object and only when allowed by the parameter
"signature" from the ADM/ODM.
The object path itself contains the components, described in the
following subsections: namespace ID, object type, and object ID.
When encoded in text form (see Section 4), the path components
correspond to the URI path segments.
3.3.1. Namespace ID
ADM resources exist within namespaces to eliminate the possibility of
a conflicting resource name, aid in the application of patterns, and
improve the compressibility of the ARI. Namespaces SHALL NOT be used
as a security mechanism to manage access. An Agent or Manager SHALL
NOT infer security information or access control based solely on
namespace information in an ARI.
Namespace IDs have two possible forms; one more human-friendly and
one more compressible:
Text form: This form corresponds with a human-readable identifier
for either an ADM or a ODM namespace. The text form is not
compressible and needs to be converted to a numeric namespace
based on a local registry. A text form namespace SHALL contain
only URI path segment characters representing valid UTF-8 text in
accordance with [RFC3629].
Numeric form: This form corresponds with a compressible value
suitable for on-the-wire encoding between Manager and Agent.
Sorting and matching numeric namespaces is also faster than text
form. A numeric form namespace SHALL be small enough to be
represented as a 64-bit signed integer.
Independent to the form of the namespace is the issuer of the
namespace, which is one of:
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ADM namespace: When a namespace is associated with an ADM, its text
form SHALL begin with an alphabetic character and its numeric form
SHALL be a positive integer. All ADM namespaces are universally
unique and, except for private or experimental use, SHOULD be
registered with IANA (see Table 5).
ODM namespace: When a namespace is not associated with an ADM, its
text form SHALL begin with a bang character "!" and its numeric
form SHALL be a negative integer. These namespaces do not have
universal registration and SHALL be considered to be private use.
It is expected that runtime ODM namespaces will be allocated and
managed per-user and per-mission.
3.3.2. Object Type
Due to the flat structure of an ADM, as defined in
[I-D.ietf-dtn-amm], all managed objects are of a specific and
unchanging type from a set of available managed object types. The
preferred form for object types in text ARIs is the text name, while
in binary form it is the integer enumeration (see Section 8).
The following subsection explains the form of those object
identifiers.
3.3.3. Object ID
An object is any one of a number of data elements defined for the
management of a given application or protocol that conforms to the
ADM logical schema.
Within a single ADM or runtime namespace and a single object type,
all managed objects have similar characteristics and all objects are
identified by a single text name or integer enumeration. The
preferred form for object names in text ARIs is the text name, while
in binary form it is the integer enumeration. Any ADM-defined object
will have both name and enumeration, while a runtime-defined object
can have either but not both. Conversion between the two forms
requires access to the original ADM, and its specific revision, in
which the object was defined. A text form object name SHALL contain
only URI path segment characters representing valid UTF-8 text in
accordance with [RFC3629].
3.3.4. Parameters
The ADM logical schema allows many object types to be parameterized
when defined in the context of an application or a protocol.
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If two instances of an ADM resource have the same namespace and same
object type and object name but have different parameter values, then
those instances are unique and the ARIs for those instances MUST also
be unique. Therefore, parameters are considered part of the ARI
syntax.
The ADM logical schema defines specialized uses for the term
"parameter" to disambiguate each purpose, as defined below.
Formal Parameters:
Formal parameters define the type, name, and order of the
information that customizes an ARI. They represent the unchanging
"signature" of the parameterized object. Because ARIs represent a
_use_ of an object and not its definition, formal parameters are
not present in an ARI and instead are part of an object model.
Given Parameters:
Given parameters represent the data values used to distinguish
different instances of a parameterized object. A given parameter
is an AMM value and is represented by an ARI within the context of
a parameter list (AC) or parameter map (AM). Because of necessary
normalizing (of type and default value) based on formal
parameters, multiple given parameters can correspond with the same
meaning (see Actual Parameters below).
Additionally, there are two ways in which the value of a given
parameter can be specified: parameter-by-value and parameter-by-
name.
Parameter-By-Value: This method involves directly supplying the
value as part of the actual parameter. It is the default
method for supplying values.
Parameter-By-Name: This method involves specifying the name of an
other parameter and using that other parameter's value as a
substitute for the value of this parameter. This method is
useful when a parameterized ARI is produced by an AMM object
which itself is parameterized. The original ARI parameters
contain literal ARIs with LABEL type, and when the value is
produced based on input parameters the substitution is made.
In this way, an actual parameter can be "flowed down" to
produced values at runtime.
Actual Parameters:
Actual parameters represent a normalized set of values taken from
a set of given parameters and normalized using a set of
corresponding formal parameters. An actual parameter is an AMM
value and is represented by an ARI.
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Because normalizing can cause a given parameter to change type (in
order to conform to a formal parameter type) or take on a default
value (when not present in the given parameters), a single set of
actual parameters can correspond with multiple options for given
parameters.
3.4. Namespace References
A namespace reference is composed of a single part, the namespace ID,
which is used to refer to an entire ADM or ODM. It is treated as a
separate class of ARI in order to separate it from the additional
required parts of an Object Reference (object type and object ID).
The purpose of a namespace reference is to give an ARI value to the
whole namespace separately from any of its contained objects.
4. ARI Text Form
This section defines how the data model explained in Section 3 is
encoded as text conforming to the URI syntax of [RFC3986]. The most
straightforward text form of ARI uses an explicit scheme and an
absolute path (starting with an initial slash "/"), which requires no
additional context to interpret its structure.
When used within the context of a base ARI, the URI Reference form of
Section 4.5 can be used. In all other cases an ARI must be an
absolute-path form and contain a scheme.
While this text description is normative, the ABNF schema in this
section provides a more explicit and machine-parsable text schema.
The scheme name of the ARI is "ari" and the scheme-specific part of
the ARI follows one of the two forms corresponding to the literal-
value ARI and the object reference ARI.
ari = [ARIPREFIX] ari-ssp
ari-ssp = lit-ssp-struct / objref-ssp-struct / nsref-ssp-struct
; restricted to only a subset of "ari" symbol
lit-ari = [ARIPREFIX] lit-ssp-struct
objref-ari = [ARIPREFIX] objref-ssp-struct
ARIPREFIX = "ari:"
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4.1. URIs and Percent Encoding
Due to the intrinsic structure of the URI, on which the text form of
ARI is based, there are limitations on the syntax available to the
scheme-specific-part [RFC7595]. One of these limitations is that
each path segment can contain only characters in the pchar ABNF
symbol defined in [RFC3986]. For most parts of the ARI this
restriction is upheld by the values themselves: ADM/ODM names,
literal and object type names, and object names have a limited
character set all within the symbol val-seg. For literals and nested
parameters though, the percent encoding of Section 2.4 of [RFC3986]
is needed.
The following symbol val-seg is an allowed superset of all path
segment patterns, which includes ARI-specific control characters.
; A subset of RFC 3986 segment-nz and pchar symbols which matches all
; identifiers, primitive values, and typed-literal values
val-seg = 1*( unreserved / pct-encoded / val-delims)
val-delims = "!" / "'" / "+" / ":" / "@"
; A text name must start with an alphabetic character or underscore
id-text = (ALPHA / "_") *(ALPHA / DIGIT / "_" / "-" / ".")
; An integer enum must contain only digits with no zero padding
id-num = nopad-number
nopad-number = "0" / non-zero-number
non-zero-number = %x31-39 *DIGIT
DIGIT = %x30-39
In the ARI text examples in this document the URIs have been percent-
decoded for clarity, as might be done in an ARI display and editing
tool. But the actual encoded form of the human-friendly ARI
ari:"text" is ari:%22text%22. Outside of literals, the safe
characters which are not be percent-encoded are the structural
delimiters /()=;, used for parameters and ARI collections.
| Even with the allowed character set of val-seg there are still
| some literal value control characters that do not fit within
| the URI pchar set and which need to be percent-encoded,
| specifically the double-quote character " and the embedded CBOR
| brackets << and >>.
One other aspect of convenience for human editing of text-form ARIs
is linear white space. The current ABNF pattern, staying within the
URI pattern, do not allow for whitespace to separate list items or
otherwise. A human editing an ARI could find it convenient to
include whitespace following commas between list items, or to
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separate large lists across lines. Any tool that allows this kind of
convenience of editing SHALL collapse any white space within a single
ARI before encoding its contents.
4.2. Literals
Based on the structure of Section 3.2, the text form of the literal
ARI contains only a URI path with an optional AMM literal type. A
literal has no concept of a namespace or context, so the path is
always absolute. When the path has two segments, the first is the
AMM literal type and the second is the encoded literal value. When
the path has a single segment it is the encoded literal value. As a
shortcut, an ARI with only a single path segment is necessarily an
untyped literal so the leading slash is elided.
The text form of literal ARI has two layers of coding: the URI path
structure and the type-specific value coding. These are
distinguished below in the ABNF by the lit-ssp-struct symbol being
for the general path structure and type-specific coding defined in
Section 4.2.1.
lit-ssp-struct = lit-container / lit-typeval-struct
/ lit-notype-struct
; More complex text for non-primitive values
lit-typeval-struct = "/" lit-type "/" val-seg
; Type is restricted to valid literal types, within the "val-seg" set
lit-type = id-text / id-num
; Containers use different structure than lit-typeval-struct
; because of rule recursion
lit-container = lit-ac / lit-am / lit-tbl / lit-execset / lit-rptset
lit-ac = "/" ("AC" / "17") "/" ari-collection
lit-am = "/" ("AM" / "18") "/" ari-map
lit-tbl = "/" ("TBL" / "19") "/" ari-tbl
lit-execset = "/" ("EXECSET" / "20") "/" exec-set
lit-rptset = "/" ("RPTSET" / "21") "/" rpt-set
; The untyped value is a subset of the "lit-notype" symbol
lit-notype-struct = val-seg
4.2.1. Typed Literal Values
The definition in this section is a specialization of the lit-
typeval-struct structure for specific literal types.
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An ARI encoder or decoder SHALL handle both text name and integer
enumeration forms of the lit-type symbol. When present and able to
be looked up, the literal type SHOULD be a text name.
The text form of typed values SHALL be one of the following, based on
the associated lit-type value in the ARI:
NULL:
This type contains only the single the fixed value "null".
null = "null"
BOOL:
This type contains the two fixed values "true" and "false".
bool = "true" / "false"
BYTE, INT, UINT, VAST, or UVAST:
The integer types, signed or unsigned, match the following integer
ABNF symbol. Each specific type will limit the domain of valid
values within this more general encoding.
integer = int-dec / int-bin / int-hex
int-dec = optsign 1*DIGIT
int-bin = optsign "0b" 1*BIT
int-hex = optsign "0x" 1*HEXDIG
optsign = ["+" / "-"]
REAL32 or REAL64:
The floating-point types match the following float ABNF symbol,
which includes a hexadecimal form that avoids decimal conversion
of the underlying value. All of these forms conform to the text
representations defined in Section 5.12 of [IEEE.754-2019] for
binary16, binary32, or binary64 values.
float = float-exp / float-dec / float-hex
; Decimal exponential corresponds with C99 '%e' format
float-exp = optsign 1*DIGIT ["." 1*DIGIT] "e" optsign 1*DIGIT
; Decimal fraction corresponds with C99 '%f' format
float-dec = optsign 1*DIGIT "." *DIGIT
; Hexadecimal exponential corresponds with C99 '%a' format
float-hex = optsign "0x" 1*HEXDIG "." *HEXDIG
["p" optsign 1*DIGIT]
TEXTSTR:
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The text string type matches the following tstr ABNF symbol after
percent-decoding, which is consistent with the CBOR EDN
definition. As an alternative, if the text value matches the id-
text character set it can be encoded directly without quoting.
tstr = tstr-quoted / id-text
; double-quoted and escaped text logic from Section 7 of RFC 8259
tstr-quoted = DQUOTE *char DQUOTE
DQUOTE = %x22
BYTESTR:
The byte string type matches the following bstr ABNF symbol after
percent-decoding, which is consistent with the CBOR EDN definition
restricted to only utf8, base16, and base64url encodings. The
non-prefixed form of byte string SHALL only be used if the value
contains UTF-8 text in accordance with [RFC3629]. When using the
"h" prefix the base16 encoding from Section 8 of [RFC4648] SHALL
be used. When using the "b64" prefix only the base64url encoding
from Section 5 of [RFC4648] SHALL be used as this avoids
unnecessary percent encodings.
bstr = bstr-utf8 / bstr-b16 / bstr-b64
; Escaped text logic from Section 7 of RFC 8259
bstr-utf8 = SQUOTE *char SQUOTE
; Encoding of Section 8 of RFC 4648
bstr-b16 = "h" SQUOTE *(2HEXDIG) SQUOTE
; Encoding of Section 5 of RFC 4648
bstr-b64 = "b64" SQUOTE *(ALPHA / DIGIT / "-" / "_") *EQ SQUOTE
SQUOTE = %x27
EQ = %x3D
TP:
This type uses either the date-time ABNF symbol of Appendix A of
[RFC3339] always in the "Z" time-offset, or as a decimal
representation of the relative time from the DTN Epoch. This text
is unquoted and, to avoid percent encoding, this text form MAY
omit the separator characters "-" and ":".
tp-val = date-time / float-dec / integer
TD:
This type uses either the duration ABNF symbol of Appendix A of
[RFC3339] with a positive or negative sign prefix, or as a decimal
representation of the relative time value. This text is unquoted
and due to the constraints on the value need not be percent
encoded.
td-val = duration / float-dec / integer
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LABEL:
This type uses the following lit-label ABNF symbol from this
document. This text is unquoted and due to the constraints on the
value need not be percent encoded.
lit-label = id-text / id-num
CBOR:
This type uses the following emb-cbor ABNF symbol for its value.
The first encoding choice uses the percent encoded form of CBOR
extended diagnostic notation (EDN) of Appendix G of [RFC8610].
The second encoding is the raw byte string of the embedded CBOR.
emb-cbor = cbor-diag / bstr
cbor-diag = "<<" *(%x20-3B / %x3D / %x3F-7E) ">>"
AC:
This type uses the following ari-collection ABNF symbol for its
value. Each item of the collection is an already-percent-encoded
text-form ARI.
; A comma-separated list of any form of ARI with enclosure
ari-collection = "(" [ari-collection-list] ")"
ari-collection-list = ari *("," ari)
AM:
This type uses the following ari-map ABNF symbol for its value.
Each key of the map is an already-percent-encoded text-form
literal-value ARI. Each value of the map is an already-percent-
encoded text-form ARI.
; A comma-separate list of pairs, each delimited by equal-sign
; with literal-only keys
ari-map = "(" [ari-map-list] ")"
ari-map-list = ari-map-pair *("," ari-map-pair)
ari-map-pair = lit-notype "=" ari
TBL:
This type uses the following ari-tbl ABNF symbol for its value.
The value is prefixed by the number of columns in the table,
followed by an AC representing each separate row in the table.
Each item of the table is an already-percent-encoded text-form
ARI.
ari-tbl = "c=" nopad-number ";" *ari-collection
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| Note that although the TBL uses the same syntax as AC for
| encoding each row, the value itself is not necessarily
| internally represented by a sequence of AC values.
EXECSET:
This type uses the following exec-set ABNF symbol for its value.
The value is prefixed by the optional nonce value for the
associated execution(s), followed by an AC representing each item
to be executed (either a CTRL reference, MAC-producing reference,
or MAC value). Each item of the targets is an already-percent-
encoded text-form ARI.
exec-set = "n=" exec-nonce ";" exec-targets
exec-nonce = null / integer / bstr
exec-targets = ari-collection
| Note that although the EXECSET uses the same syntax as AC
| for encoding each row, the value itself is not necessarily
| internally represented by an AC.
RPTSET:
This type uses the following rpt-set ABNF symbol for its value.
The value consists of the optional nonce value for the associated
execution(s), a reference absolute time for all contained reports,
and the list of contained reports. Each contained report consists
of a relative creation time for the report (relative to the RPTSET
reference time), a reference to the source of the report, and an
AC representing each item in the report. Each item of a report is
an already-percent-encoded text-form ARI, as is the source
reference. The nonce and timestamps are all literal values
constained to specific value types.
rpt-set = "n=" exec-nonce ";r=" lit-ari ";" *rpt-container
rpt-container = "(t=" lit-ari ";s=" objref-ari ";" rpt-items ")"
rpt-items = ari-collection
| Note that although the report container uses the same syntax
| as AC for encoding each row, the items itself is not
| necessarily internally represented by an AC.
Some examples of typed literal values are below. The represented
values for TP, TD, and CBOR types are the same just with different
text representations.
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ari:/BOOL/true
ari:/UINT/10
ari:/VAST/10
ari:/LABEL/name
ari:/TP/20230102T030405Z
ari:/TP/2023-01-02T03:04:05Z
ari:/TP/725943845
ari:/TD/+PT1H
ari:/TD/3600
ari:/CBOR/h'0a'
ari:/CBOR/%3C%3C10%3E%3E
These are typed container values with text form for AC and AM lists:
ari:/AC/(1,2,3)
ari:/AM/(1=2,2=4,3=9)
ari:/TBL/c=3;(1,true,%22A%22)(2,false,%22B%22)
And these are a pair of EXECSET and RPTSET with identical nonce
value:
ari:/EXECSET/n=1234;(//example-adm-a/CTRL/dothing,//example-adm-a/CONST/amacro)
ari:/RPTSET/n=1234;r=/TP/20230102T030405Z;(t=/TD/PT0S;s=//example-adm-a/CTRL/dothing;(null))(t=/TD/PT5S;s=//example-adm-a/CONST/amacro;(null))
4.2.2. Untyped Literal Values
The definition in this section is a specialization of the lit-notype-
struct structure for specific primitive types.
When untyped, the literal value SHALL be one of the primitive types
named by the lit-notype ABNF symbol below. The separate value
encodings use symbols from Section 4.2.1.
| The order of this symbol sequence is significant because the
| unquoted tstr must be matched after the enumerated types of
| undefined, null, and bool.
lit-notype = undefined / null / bool / float / integer / tstr / bstr
; the undefined value is only valid as an untyped literal
undefined = "undefined"
Some example of untyped literals are below.
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ari:undefined
ari:true
ari:1.1
ari:1.1e+06
ari:0x1.4p+3
ari:10
ari:0xA
ari:0b1010
ari:-0x10
ari:'bytes'
ari:h'6279746573'
ari:b64'Ynl0ZXM='
ari:%22text%22
ari:%22hi%5Cu1234%22
ari:%22hi%5CuD834%5CuDD1E%22
4.2.3. Preferred Encodings
Several of the literal types defined in Section 4.2.1 allow the same
AMM value to be represented by multiple logically equivalent
encodings. Because these encodings are not equivalent in represented
text size or processing needs it is useful for an ARI processor to
allow a user to determine preferred encodings when processing text-
form ARIs.
Integer values: These options correspond to the BYTE, INT, UINT,
VAST, and UVAST types and untyped int values. These values can be
encoded as either base-2, base-10, or base-16. In uses which are
more resource constrained and less human-facing a processor MAY
encode integers only in base-16.
Floating point values: These options correspond to the REAL32 and
REAL64 types and untyped float values. These values can be
encoded as either decimal fraction, decimal exponential, or
hexadecimal exponential. In uses which are more resource
constrained and less human-facing a processor MAY encode floats
only as hexadecimal.
Byte string values: These options correspond to the BYTESTR type and
untyped bstr values. These values can be encoded as either raw
bytes, base16, or base64url. In uses which are more resource
constrained and less human-facing a processor MAY encode byte
strings only as base16.
Time values: These options correspond to the TP and TD types. These
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values can be encoded as either delimited text, non-delimited
text, or decimal fraction. In uses which are more resource
constrained and less human-facing a processor MAY encode time
values only as decimal fraction.
Embedded CBOR values: These options correspond to the CBOR type.
These values can be encoded as either CBOR EDN or as a byte
string. In uses which are more resource constrained and less
human-facing a processor MAY encode CBOR values only as byte
strings.
4.3. Object References
Based on the structure of Section 3.3, the text form of the object
reference ARI is a URI with an authority, corresponding to the
namespace-id, and two path segments, corresponding to the object-type
and object-id. Those three components (excluding parameters as
defined below) are referred to as the object path.
An ARI encoder or decoder SHALL handle both text name and integer
enumeration forms of the namespace-id, object-type, and object-id.
The final segment containing the object-id MAY contain parameters
enclosed by parentheses "(" and ")". There is no semantic
distinction between the absence of parameters and the empty parameter
list. The contents of the parameters SHALL be interpreted as a
literal AC or AM in accordance with Section 4.2.
The parameters as a whole SHALL be the percent encoded form of the
constituent ARIs, excluding the structural delimiters /(),=.
Implementations are advised to be careful about the percent encoded
vs. decoded cases of each of the nested ARIs within parameters to
avoid duplicate encoding or decoding. It is recommended to dissect
the parameters and ARI collections in their encoded form first, and
then to dissect and percent decode each separately and recursively.
The object reference ARI has the following ABNF definition.
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objref-ssp-struct = obj-path [paramlist]
; The object path can be used separately than parameters
obj-path = ns-part "/" obj-type "/" obj-id
; Parameters are either AC or AM
paramlist = ari-collection / ari-map
; Absolute or relative namespace
ns-part = ("//" ns-id) / "."
; Namespace ID, within the "val-seg" set
ns-id = ns-adm / ns-odm
ns-adm = (id-text ["@" full-date]) / id-num
ns-odm = ("!" id-text) / ("-" id-num)
; Type is restricted to valid object types, within the "val-seg" set
obj-type = id-text / ("-" id-num)
; Object ID, within the "val-seg" set
obj-id = id-text / id-num
Some examples of object reference values are below.
ari://example-adm-a@2024-06-25/EDD/someobj
ari://example-adm-a/EDD/someobj
ari://example-adm-a/CTRL/otherobj(true,3)
ari://example-adm-a/CTRL/otherobj(%22a%20param%22,/UINT/10)
ari://65536/-1/0
ari://!example-odm-b/VAR/counter
ari://-20/-11/84
4.4. Namespace References
Based on the structure of Section 3.4, the text form of the namespace
reference ARI is a URI with one path segment, corresponding to the
namespace ID, followed by a path separator. The path separator is
necessary to distinguish this from a untyped literal value.
The namespace reference ARI has the following ABNF definition.
nsref-ssp-struct = "//" ns-id "/"
Some examples of namespace reference values are below.
ari://example-adm-a@2024-06-25/
ari://example-adm-a/
ari://65536/
ari://!example-odm-b/
ari://-20/
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4.5. ARI References
The text form of ARI can contain a URI Reference, as defined in
Section 3 of [RFC3986], only for the specific case of eliding the
namespace of Object Reference values. In this case, its object path
SHALL start with the relative path segment "." (see the ns-part rule
of Section 4.3).
Examples of text name and integer enumerated identifiers in an ARI
Reference are below.
ari:./CTRL/do_thing
ari:./CTRL/otherobj(%22a%20param%22,/UINT/10)
ari:./-2/30
ARI Reference resolution is discussed in Section 6.2.
5. ARI Binary Form
This section defines how the data model explained in Section 3 is
encoded as a binary sequence conforming to the CBOR syntax of
[RFC8949]. Within this section the term "item" is used to mean the
CBOR-decoded data item which follows the logical model of CDDL
[RFC8610].
The binary form of the URI is intended to be used for machine-to-
machine interchange so it is missing some of the human-friendly
shortcut features of the ARI text form from Section 4. It still
follows the same logical data model so it has a one-for-one
representation of all of the styles of text-form ARI.
While this text description is normative, the CDDL schema in this
section provides a more explicit and machine-parsable binary schema.
ari = lit-ari / objref-ari
5.1. Intermediate CBOR
The CBOR item form is used as an intermediate encoding between the
ARI data and the ultimate binary encoding. When decoding a binary
form ARI, the CBOR must be both "well-formed" according to [RFC8949]
and "valid" according to the CDDL model of this specification.
Implementations are encouraged, but not required, to use a streaming
form of CBOR encoder/decoder to reduce memory consumption of an ARI
handler. For simple implementations or diagnostic purposes, a two
stage conversion between ARI--CBOR and CBOR--binary can be more
easily understood and tested.
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5.2. Literals
Based on the structure of Section 3.2, the binary form of the literal
ARI contains a data item along with an optional AMM literal type
identifier. In order to keep the encoding as short as possible, the
untyped literal is encoded as the simple value itself. Because the
typed literal and the object reference forms uses CBOR array framing,
this framing is used to disambiguate from the pure-value encoding of
the lit-notype CDDL symbol.
When present, the literal type SHALL be an integer enumeration. When
typed, the decoded literal value SHALL be a valid CBOR item
conforming to the AMM literal type definition of the $lit-typeval
CDDL socket. When untyped, the decoded literal value SHALL be one of
the primitive types named by the lit-notype CDDL symbol.
The literal ARI, both typed and untyped, has the following CDDL
definition.
lit-ari = lit-typeval / lit-notype
; undefined value is only allowed as non-typed literal
lit-notype = undefined / null / bool / int / float / tstr / bstr
lit-typeval = $lit-typeval .within lit-typeval-struct
lit-typeval-struct = [
lit-type: lit-type-id,
lit-value: any
]
lit-type-id = (int32 .ge 0)
; IANA-assigned literal types
$lit-typeval /= [0, null]
$lit-typeval /= [1, bool]
$lit-typeval /= [2, uint .size 1] ; 1-byte
$lit-typeval /= [4, int32] ; 4-byte
$lit-typeval /= [5, uint32] ; 4-byte
$lit-typeval /= [6, int64] ; 8-byte
$lit-typeval /= [7, uint64] ; 8-byte
$lit-typeval /= [8, float16 / float32]
$lit-typeval /= [9, float16 / float32 / float64]
$lit-typeval /= [10, tstr]
$lit-typeval /= [11, bstr]
; Absolute timestamp as seconds from DTN Epoch
$lit-typeval /= [12, lit-time]
; Relative time interval as seconds
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$lit-typeval /= [13, lit-time]
lit-time = int / time-fraction
; Same structure as tag #4 "decimal fraction" but limited in domain
time-fraction = [
exp: (-9 .. 9) .within int,
mantissa: int,
]
; Parameter label
$lit-typeval /= [14, lit-label]
lit-label = int64 / id-text
; Embedded CBOR item
$lit-typeval /= [15, lit-cbor]
lit-cbor = bstr .cbor any
; Literal type ID value
$lit-typeval /= [16, lit-type-id]
; Ordered list of ARIs
$lit-typeval /= [17, ari-collection]
ari-collection = [*ari]
; Map from untyped literal to ARI
$lit-typeval /= [18, ari-map]
ari-map-key = lit-notype
ari-map = {*ari-map-key => ari}
; Table of ARIs
$lit-typeval /= [19, ari-tbl]
ari-tbl = [
ncol: uint, ; Number of columns in the table
*ari ; All rows are concatenated in the single array
]
; Execution-Set
$lit-typeval /= lit-execset
lit-execset = [20, exec-set]
exec-set = [
nonce,
exec-targets,
]
nonce = bstr / uint / null
exec-targets = (*objref-ari)
; Reporting-Set
$lit-typeval /= lit-rptset
lit-rptset = [21, rpt-set]
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rpt-set = [
nonce,
ref-time: lit-time, ; Interpreted as a TP absolute time
*rpt-container
]
rpt-container = [
rel-time: lit-time ; Interpreted as a TD relative to ref-time
source: objref-ari,
rpt-items
]
rpt-items = (*ari)
Some example of the forms for a literal are below. These first are
untyped primitive values:
true
"text"
10
And these are typed values:
[4, 10]
[15, <<10>>]
5.3. Object References
Based on the structure of Section 3.3, the binary form of the object
reference ARI is a CBOR-encoded item. An ARI SHALL be encoded as a
CBOR array with at least three items corresponding to the namespace-
id, object-type, and object-id. Those three items are referred to as
the object path. The optional fourth item of the array is the
parameter list.
The namespace-id SHALL be present only as an integer enumeration.
The object-type SHALL be present only as an integer enumeration. The
object-id SHALL be present as either a text name or an integer
enumeration. The processing of text name object path components by
an Agent is optional and SHALL be communicated to any associated
Manager prior to encoding any ARIs for that Agent.
When present, the parameters SHALL be either the ari-collection or
ari-map structure. In other words, just the value-portion of the AC
or AM typed literal because no other disambiguation needs to be made
for the parameter type.
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The object reference ARI has the following CDDL definition.
; Type-agnostic structure of object reference
objref-ari = $objref-ari .within objref-ari-struct
objref-ari-struct = [
ns-id,
obj-type-id,
obj-id,
?params
]
; Path for a single object
obj-path<obj-type> = (
ns-id,
obj-type,
obj-id,
)
; The null ns-id means an ARI Reference
ns-id = int64 / id-text / null
; The null obj-type-id and obj-id mean a Namespace Reference
obj-type-id = (int32 .lt 0) / id-text / null
obj-id = (int32 .ge 0) / id-text / null
params = ari-collection / ari-map
; Generic usable for restricting objref-ari by type
objref-type<obj-type> = [
obj-path<obj-type>,
?params
]
; IANA-assigned object types
IDENT = -1
$objref-ari /= objref-type<IDENT>
CONST = -2
$objref-ari /= objref-type<CONST>
CTRL = -3
$objref-ari /= objref-type<CTRL>
EDD = -4
$objref-ari /= objref-type<EDD>
OPER = -6
$objref-ari /= objref-type<OPER>
SBR = -8
$objref-ari /= objref-type<SBR>
TBR = -10
$objref-ari /= objref-type<TBR>
VAR = -11
$objref-ari /= objref-type<VAR>
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TYPEDEF = -12
$objref-ari /= objref-type<TYPEDEF>
An example object reference without parameters is:
[41, -1, 0]
Another example object reference with parameters is:
[41, -2, 3, ["a param", [4, 10]]]
5.3.1. Namespace References
Based on the structure of Section 3.4, the binary form of the
namespace reference ARI is a specialization of the object reference
encoding as defined below.
nsref-ari = [ns-id, null, null] .within objref-ari-struct
Some examples of namespace reference values are below.
["example-adm-a@2024-06-25", null, null]
["example-adm-a", null, null]
[65536, null, null]
["!example-odm-b", null, null]
[-20, null, null]
5.3.2. ARI References
The binary form of ARI includes the ability to encode a URI Reference
only for the specific case of eliding the namespace of Object
Reference values. In this case the namespace portion of an object
path is replaced by the CBOR value null as defined below.
ariref-ari = [null, obj-type-id, obj-id, ?params] .within objref-ari-struct
Examples of text name and integer enumerated identifiers in an ARI
Reference are below.
[null, "CTRL", "do_thing"]
[null, -2, 30]
ARI Reference resolution is discussed in Section 6.2.
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6. Processing Activities
Separate from the forms of encoding the ARI information, there are
some ARI-specific processing activities that can be used to transform
one ARI value into another without changing the higher-level meaning
of the value. Both of these activities require an external context
to work in a meaningful way.
6.1. ID Segment Translation
Because both the text and binary form of the ARI allow ID segments to
contain either a text name or an integer enumeration, ARIs can be
translated one-for-one between the two forms without loss.
When translating literal types into text form and code point lookup
tables are available, the literal type SHOULD be converted to its
text name. When translating literal types from text form and code
point lookup tables are available, the literal type SHOULD be
converted from its text name. The conversion between AMM literal
type name and enumeration requires a lookup table based on the
registrations in Table 2.
When translating object references into text form and code point
lookup tables are available, any enumerated item SHOULD be converted
to its text name. When translating object references from text form
and code point lookup tables are available, any enumerated item
SHOULD be converted from its text name. The conversion between AMM
object-type name and enumeration requires a lookup table based on the
registrations in Table 3. The conversion between name and
enumeration for either namespace-id or object-id require lookup
tables based on ADMs and ODMs known to the processing entity.
6.2. ARI Reference Resolution
Resolving an ARI Reference (where an object reference namespace is
elided) SHALL consist of replacing the namespace component with the
namespace of the resolving context. ARI Reference resolution SHALL
apply to any nested values in literal containers or in object
reference parameters.
7. ARI Patterns
Because the ARI logical structure (Section 3) uses path segments to
delimit the components of the absolute path, and due to the
restrictions of the ARI path segment content, it is possible for URI
reserved characters to be able to provide wildcard-type patterns.
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Although the form is similar, an ARI Pattern is not itself an ARI and
they cannot be used interchangeably. The context used to interpret
and match an ARI Pattern SHALL be explicit and separate from that
used to interpret and dereference an ARI.
While an ARI is used to dereference to a specific managed object and
invoke behavior on that object, an ARI Pattern is used solely to
perform matching logic against text-form ARIs. The ARI Pattern SHALL
NOT ever take the form of a URI Reference; only as an absolute URI.
An ARI Pattern SHALL NOT ever contain parameters, only object path.
An ARI Pattern has no optional path segments. When used as a literal
ARI pattern the path SHALL have two segments. When used as an object
reference ARI pattern the path SHALL have three segments.
The single-wildcard is the only defined segment pattern and a segment
can either be a real ID or a single wildcard. Because an ARI Pattern
is just used to match text-form ARIs it has no specific restrictions
on enumerated segment text the way a valid ARI does.
The ABNF for the ARI Pattern is given here:
ari-pat = "ari:" ari-pat-ssp
ari-pat-ssp = ari-pat-literal / ari-pat-objref
ari-pat-literal = "/" id-pat "/" id-pat
ari-pat-objref = "//" id-pat "/" id-pat "/" id-pat
; The non-wildcard rule is the same as ARI syntax
id-pat = wildcard / val-seg
wildcard = "*"
7.1. ARI Matching
An ARI Pattern SHALL be considered to match an ARI when, after
removing the ARI's parameters, each component of the ARI Pattern
matches the corresponding ARI path component. Each pattern component
SHALL be considered to match according to the following rules:
Specific value: The pattern component SHALL be compared with the ARI
component after both are percent-decoded in accordance with
Section 2.1 of [RFC3986] and UTF-8 decoded in accordance with
[RFC3629].
Single-segment wildcard: The pattern component SHALL be considered
to match with any ARI component, if present, including an empty
component.
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8. Transcoding Considerations
When translating literal values into text form, it is necessary to
canonicalize the CBOR extended diagnostic notation of the item. The
following applies to generating text form from CBOR items:
* Only the outermost value SHALL contain the "ari:" scheme prefix.
This applies to cases of either literal container types or object
reference parameter values.
* The canonical presentation form of CBOR null and bool values SHALL
be the names identified in Section 8 of [RFC8949].
* The canonical presentation form of CBOR int and float values SHALL
be the decimal encoding defined in Section 8 of [RFC8949].
* The canonical presentation form of CBOR tstr values SHALL be the
definite-length, non-concatenated encoding defined in Section 8 of
[RFC8949].
* The canonical presentation form of CBOR bstr values SHALL be the
definite-length, base16 ("h" prefix), non-concatenated encoding
defined in Section 8 of [RFC8949].
* The canonical presentation form for literal type TP values SHALL
be the human-friendly date-time encoding.
* The canonical presentation form for literal type TD values SHALL
be the human-friendly duration encoding.
* When canonical presentation form for literal type CBOR values
SHALL be the embedded CBOR encoding defined in Appendix G.3 of
[RFC8610].
9. Interoperability Considerations
DTN challenged networks might interface with better resourced
networks that are managed using non-DTN management protocols. When
this occurs, the federated network architecture might need to define
management gateways that translate between DTN and non-DTN management
approaches.
| NOTE: It is also possible for DTN management be used end-to-end
| because this approach can also operate in less challenged
| networks. The opposite is not true; non-DTN management
| approaches should not be assumed to work in DTN challenged
| networks.
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Where possible, ARIs should be translatable to other, non-DTN
management naming schemes. This translation might not be 1-1, as the
features of the ADM may differ from features in other management
naming schemes. Therefore, it is unlikely that a single naming
scheme can be used for both DTN and non-DTN management.
10. Security Considerations
Because ADM and ODM namespaces are defined by any entity, no security
or permission meaning can be inferred simply from the expression of
namespace.
11. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of schema and namespaces
related to ARIs, in accordance with BCP 26 [RFC1155].
11.1. URI Schemes Registry
This document defines a new URI scheme "ari" in Section 4. A new
entry has been added to the "URI Schemes" registry [IANA-URI] with
the following parameters.
Scheme name:
ari
Status:
Permanent
Applications/protocols that use this scheme name:
The scheme is used by DTNMA Managers and Agents to identify
managed objects.
Contact:
IETF Chair <chair@ietf.org>
Change controller:
IESG <iesg@ietf.org>
Reference:
Section 4 of [This document].
11.2. DTN Management Architecture Parameters
This document defines several new registries within the "DTN
Management Architecture Parameters" registry group.
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This document defines a new registry "Literal Types" within the "DTN
Management Architecture Parameters" registry group [IANA-DTNMA]
containing initial entries from Table 2. Enumerations in this
registry SHALL be non-negative integers representable as CBOR uint
type with an argument shorter than 4-bytes. Names in this registry
SHALL be unique among all entries in this and the "Managed Object
Types" registry. The registration procedure for the Literal Types
registry is Specification Required.
+=============+=========+==============================+===========+
| Enumeration | Name | Description | Reference |
+=============+=========+==============================+===========+
| _0_ | NULL | The singleton null value. | [This |
| | | | document] |
+-------------+---------+------------------------------+-----------+
| _1_ | BOOL | A native boolean true or | [This |
| | | false value. | document] |
+-------------+---------+------------------------------+-----------+
| _2_ | BYTE | An 8-bit unsigned integer. | [This |
| | | | document] |
| | | The valid domain is 0 to | |
| | | 2^8-1 inclusive. | |
+-------------+---------+------------------------------+-----------+
| _4_ | INT | A 32-bit signed integer. | [This |
| | | | document] |
| | | The valid domain is -2^31 to | |
| | | 2^31-1 inclusive | |
+-------------+---------+------------------------------+-----------+
| _5_ | UINT | A 32-bit unsigned integer. | [This |
| | | | document] |
| | | The valid domain is 0 to | |
| | | 2^32-1 inclusive | |
+-------------+---------+------------------------------+-----------+
| _6_ | VAST | A 64-bit signed integer. | [This |
| | | | document] |
| | | The valid domain is -2^63 to | |
| | | 2^63-1 inclusive | |
+-------------+---------+------------------------------+-----------+
| _7_ | UVAST | A 64-bit unsigned integer. | [This |
| | | | document] |
| | | The valid domain is 0 to | |
| | | 2^64-1 inclusive | |
+-------------+---------+------------------------------+-----------+
| _8_ | REAL32 | A 32-bit [IEEE.754-2019] | [This |
| | | floating point number. | document] |
+-------------+---------+------------------------------+-----------+
| _9_ | REAL64 | A 64-bit [IEEE.754-2019] | [This |
| | | floating point number. | document] |
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+-------------+---------+------------------------------+-----------+
| _10_ | TEXTSTR | A text string composed of | [This |
| | | (unicode) characters in | document] |
| | | accordance with [RFC3629]. | |
+-------------+---------+------------------------------+-----------+
| _11_ | BYTESTR | A byte string composed of | [This |
| | | 8-bit values. | document] |
+-------------+---------+------------------------------+-----------+
| _12_ | TP | An absolute time point (TP) | [This |
| | | in the DTN Epoch of | document] |
| | | Section 4.2.6 of [RFC9171]. | |
+-------------+---------+------------------------------+-----------+
| _13_ | TD | A relative time difference | [This |
| | | (TD) with a sign. | document] |
+-------------+---------+------------------------------+-----------+
| _14_ | LABEL | A text label of a parent | [This |
| | | object parameter. This is | document] |
| | | only valid in a nested | |
| | | parameterized ARI. | |
+-------------+---------+------------------------------+-----------+
| _15_ | CBOR | A byte string containing an | [This |
| | | encoded CBOR item. The | document] |
| | | structure is opaque to the | |
| | | Agent but guaranteed well- | |
| | | formed for the ADM using it. | |
+-------------+---------+------------------------------+-----------+
| _16_ | ARITYPE | An integer or text value | [This |
| | | representing one of the code | document] |
| | | points in this Literal Types | |
| | | registry or the Managed | |
| | | Object Types registry. | |
+-------------+---------+------------------------------+-----------+
| _17_ | AC | An array containing an | [This |
| | | ordered list of ARIs. | document] |
+-------------+---------+------------------------------+-----------+
| _18_ | AM | A map containing keys of | [This |
| | | primitive ARIs and values of | document] |
| | | ARIs. | |
+-------------+---------+------------------------------+-----------+
| _19_ | TBL | A two-dimensional table | [This |
| | | containing cells of ARIs. | document] |
+-------------+---------+------------------------------+-----------+
| _20_ | EXECSET | A structure containing | [This |
| | | values to be executed by an | document] |
| | | Agent. | |
+-------------+---------+------------------------------+-----------+
| _21_ | RPTSET | A structure containing | [This |
| | | reports of values sampled | document] |
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| | | from an Agent. | |
+-------------+---------+------------------------------+-----------+
| 22 to 254 | | _Unassigned_ | |
+-------------+---------+------------------------------+-----------+
| _255_ | LITERAL | A reserved type name for the | [This |
| | | union of all possible | document] |
| | | literal types. | |
+-------------+---------+------------------------------+-----------+
| 256 to | | _Unassigned_ | |
| 65279 | | | |
+-------------+---------+------------------------------+-----------+
| 65280 to | | Enumerations that are | [This |
| 2147483647 | | 2**16-2**8 and larger are | document] |
| | | reserved for private or | |
| | | experimental use. | |
+-------------+---------+------------------------------+-----------+
Table 2: Literal Types
This document defines a new registry "Managed Object Types" within
the "DTN Management Architecture Parameters" registry group
[IANA-DTNMA] containing initial entries from Table 3. Enumerations
in this registry SHALL be negative integers representable as CBOR
nint type with an argument shorter than 4-bytes. Names in this
registry SHALL be unique among all entries in this and the "Literal
Types" registry. The registration procedure for the Managed Object
Types registry is Specification Required.
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+=============+=========+============================+===========+
| Enumeration | Name | Description | Reference |
+=============+=========+============================+===========+
| _-1_ | IDENT | Identity Object | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-2_ | CONST | Constant | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-3_ | CTRL | Control | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-4_ | EDD | Externally Defined Data | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-6_ | OPER | Operator | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-8_ | SBR | State-Based Rule | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-10_ | TBR | Time-Based Rule | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-11_ | VAR | Variable | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| _-12_ | TYPEDEF | Named semantic type | [This |
| | | | document] |
+-------------+---------+----------------------------+-----------+
| -13 to -255 | | _Unassigned_ | |
+-------------+---------+----------------------------+-----------+
| _-256_ | OBJECT | A reserved type name for | [This |
| | | the union of all possible | document] |
| | | object types. | |
+-------------+---------+----------------------------+-----------+
| -257 to | | _Unassigned_ | |
| -65280 | | | |
+-------------+---------+----------------------------+-----------+
| -65281 to | | Enumerations that are | [This |
| -2147483648 | | -1-(2**16-2**8) and larger | document] |
| | | are reserved for private | |
| | | or experimental use. | |
+-------------+---------+----------------------------+-----------+
Table 3: Managed Object Types
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IANA has annotated the "Literal Types" and "Managed Object Types"
registries with the following note:
| The enumeration and name of all entries managed by IANA are unique
| acorss both the "Literal Types" and "Managed Object Types"
| registries.
This document defines a new registry "Application Data Models" within
the "DTN Management Architecture Parameters" registry group
[IANA-DTNMA] containing initial entries from Table 5. Enumerations
in this registry are non-negative integers representable as CBOR uint
type with an argument shorter than 8-bytes. The registration
procedures for this registry are indicated in Table 4.
+===================+=====================================+
| Enumeration Range | Registration Procedure |
+===================+=====================================+
| 1 to 24 | Standards Action With Expert Review |
+-------------------+-------------------------------------+
| 25 to 255 | Private Use |
+-------------------+-------------------------------------+
| 256 to 4294967296 | Specification Required |
+-------------------+-------------------------------------+
Table 4: Application Data Models Registration Procedures
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+=============+======+===========+==============================+
| Enumeration | Name | Reference | Notes |
+=============+======+===========+==============================+
| 0 | | [This | Value zero is reserved. |
| | | document] | |
+-------------+------+-----------+------------------------------+
| 1 to 24 | | | _Unassigned_ |
+-------------+------+-----------+------------------------------+
| 25 to 255 | | [This | Enumerations with 8-bit size |
| | | document] | are reserved for Private Use |
+-------------+------+-----------+------------------------------+
| 256 to | | | _Unassigned_ |
| 65535 | | | |
+-------------+------+-----------+------------------------------+
| 65536 to | | [This | Reserved for example ADMs |
| 65546 | | document] | |
+-------------+------+-----------+------------------------------+
| 65547 to | | | _Unassigned_ |
| 4294967296 | | | |
+-------------+------+-----------+------------------------------+
| 4294967296 | | [This | Enumerations that are larger |
| and larger | | document] | than 32-bit are reserved for |
| | | | private or experimental use. |
+-------------+------+-----------+------------------------------+
Table 5: Application Data Models
12. References
12.1. Normative References
[IANA-DTNMA]
IANA, "Delay-Tolerant Networking Management Architecture
(DTNMA) Parameters",
<https://www.iana.org/assignments/TBA/>.
[IANA-URI] IANA, "Uniform Resource Identifier (URI) Schemes",
<https://www.iana.org/assignments/uri-schemes/>.
[IEEE.754-2019]
IEEE, "IEEE Standard for Floating-Point Arithmetic",
IEEE IEEE 754-2019, DOI 10.1109/IEEESTD.2019.8766229, 18
July 2019, <https://ieeexplore.ieee.org/document/8766229>.
[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>.
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[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>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[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>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
and Registration Procedures for URI Schemes", BCP 35,
RFC 7595, DOI 10.17487/RFC7595, June 2015,
<https://www.rfc-editor.org/info/rfc7595>.
[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>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[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>.
[RFC9171] Burleigh, S., Fall, K., and E. Birrane, III, "Bundle
Protocol Version 7", RFC 9171, DOI 10.17487/RFC9171,
January 2022, <https://www.rfc-editor.org/info/rfc9171>.
[I-D.ietf-dtn-amm]
Birrane, E. J., Sipos, B., and J. Ethier, "DTNMA
Application Management Model (AMM) and Data Models", Work
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in Progress, Internet-Draft, draft-ietf-dtn-amm-00, 3 July
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
dtn-amm-00>.
12.2. Informative References
[IEEE.1003.1-2024]
IEEE, "IEEE/Open Group Standard for Information
Technology--Portable Operating System Interface (POSIX™)
Base Specifications, Issue 8", IEEE 1003-1-2024,
DOI 10.1109/IEEESTD.2024.10555529, 13 June 2024,
<https://ieeexplore.ieee.org/document/10555529>.
[ISO.9899-1999]
ISO, "Programming Languages -- C", ISO/IEC 9899:1999,
December 1999, <https://www.iso.org/standard/29237.html>.
[RFC1155] Rose, M. and K. McCloghrie, "Structure and identification
of management information for TCP/IP-based internets",
STD 16, RFC 1155, DOI 10.17487/RFC1155, May 1990,
<https://www.rfc-editor.org/info/rfc1155>.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
Networking Architecture", RFC 4838, DOI 10.17487/RFC4838,
April 2007, <https://www.rfc-editor.org/info/rfc4838>.
[RFC7320] Nottingham, M., "URI Design and Ownership", RFC 7320,
DOI 10.17487/RFC7320, July 2014,
<https://www.rfc-editor.org/info/rfc7320>.
[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>.
[RFC8820] Nottingham, M., "URI Design and Ownership", BCP 190,
RFC 8820, DOI 10.17487/RFC8820, June 2020,
<https://www.rfc-editor.org/info/rfc8820>.
[I-D.ietf-dtn-dtnma]
Birrane, E. J., Heiner, S., and E. Annis, "DTN Management
Architecture", Work in Progress, Internet-Draft, draft-
ietf-dtn-dtnma-14, 28 April 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-dtn-
dtnma-14>.
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Appendix A. Example Equivalences
This section contains examples of converting between text name and
integer enumeration of ARI components and converting between text
form and binary form of entire ARIs. The examples in this section
rely on the ADM and ODM definitions in Table 6 and Table 7
respectively.
+=============+===============+
| Enumeration | Name |
+=============+===============+
| 65536 | example-adm-a |
+-------------+---------------+
| 65537 | example-adm-b |
+-------------+---------------+
Table 6: Example ADMs
+=============+=======+
| Enumeration | Name |
+=============+=======+
| -10 | odm10 |
+-------------+-------+
Table 7: Example ODMs
Given those namespaces, the example objects are listed in Table 8
where the Namespace column uses the ARI text form convention.
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+===============+=======+=============+================+===========+
| Namespace |Object | Enumeration | Name | Signature |
| |Type | | | |
+===============+=======+=============+================+===========+
| example-adm-a |EDD | 3 | num_bytes | () |
+---------------+-------+-------------+----------------+-----------+
| example-adm-a |CTRL | 2 | do_thing | (AC |
| | | | | targets, |
| | | | | UINT |
| | | | | count) |
+---------------+-------+-------------+----------------+-----------+
| example-adm-a |CONST | 1 | rpt_with_param | (ARI var, |
| | | | | TEXTSTR |
| | | | | text) |
+---------------+-------+-------------+----------------+-----------+
| example-adm-a |TYPEDEF| 1 | distance | () |
+---------------+-------+-------------+----------------+-----------+
| !odm10 |VAR | 1 | my_counter | () |
+---------------+-------+-------------+----------------+-----------+
Table 8: Example Objects
The TYPEDEF distance is defined to be an augmented use of uint with
scale of 1.0 and unit of meter.
Each of the following examples illustrate the comparison of ARI forms
in different situations, covering the gamut of what can be expressed
by an ARI.
A.1. Primitive-Typed Literal
This is the literal value 4 interpreted as a 32-bit unsigned integer.
The ARI text (which is identical to its percent-encoded form) is:
ari:/UINT/4
which is translated to enumerated form:
ari:/5/4
and converted to CBOR item:
[5, 4]
and finally to the binary string of:
0x820504
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A.2. Timestamp Literal
This is the timestamp "2000-01-01T00:16:40Z" which is DTN Epoch plus
1000 seconds. The ARI text (which is identical to its percent-
encoded form) is:
ari:/TP/20000101T001640Z
which is translated to enumerated form:
ari:/12/1000
and converted to CBOR item:
[12, 1000]
and finally to the binary string of:
0x820c1a000f4240
A.3. Semantic-Typed Literal
This is the literal value 20 interpreted as a semantic type distance
from example-adm-a. The ARI text (which is identical to its percent-
encoded form) is:
ari://example-adm-a/TYPEDEF/distance(20)
which is translated to enumerated form:
ari://65536/-12/1(20)
and converted to CBOR item:
[65536, -12, 1, [20]]
and finally to the binary string of:
0x841A000100002B018114
A.4. Complex CBOR Literal
This is a literal value embedding a complex CBOR structure. The CBOR
diagnostic expression being encoded is
<<{"test": [3, 4.5]}>>
which can be directly percent encoded as
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ari:/CBOR/%3C%3C%7B%22test%22%3A%5B3%2C4.5%5D%7D%3E%3E
The embedded item can further be CBOR-encoded to a byte string and
percent-encoded, along with a translated type enumeration of:
ari:/15/h'A164746573748203F94480'
and converted to CBOR item (note the byte string is no longer text-
encoded):
[15, h'A164746573748203F94480']
and finally to the binary string of:
0x820F4BA164746573748203F94480
A.5. Non-parameterized Object Reference
This is a non-parameterized num_bytes object in the ADM namespace.
The ARI text (which is identical to its percent-encoded form) is:
ari://example-adm-a/edd/num_bytes
which is translated to enumerated form:
ari://65536/-4/3
and converted to CBOR item:
[65536, -4, 3]
and finally to the binary string of:
0x831A000100002303
A.6. Parameterized Object Reference
This is an parameterized do_thing object in the ADM namespace.
Additionally, the parameters include two relative-path ARI References
to other objects in the same ADM, which are resolved after text-
decoding. The ARI text (which is identical to its percent-encoded
form) is:
ari://example-adm-a/ctrl/do_thing(/AC/(),3)
ari://example-adm-a/ctrl/do_thing(/AC/(./edd/num_bytes,//!odm10/var/my_counter),3)
which is translated to enumerated and resolved form:
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ari://65536/-3/2(/17/(//65536/-4/3,//-10/-11/1),3)
and converted to CBOR item:
[65536, -3, 2, [
[17, [
[65536, -4, 3],
[-10, -11, 1]
]],
3
]]
and finally to the binary string of:
0x841A00010000220282821182831A00010000230383292A0103
A.7. Recursive Structure with Percent Encodings
This is a complex example having nested ARIs, some with percent-
encoding needed. The human-friendly (but not valid URI) text for
this case is:
ari://example-adm-a/rptt/rpt_with_param("text")
which is percent encoded to the real URI:
ari://example-adm-a/rptt/rpt_with_param(%22text%22)
which is translated to enumerated form:
ari://65536/-7/1(%22text%22)
and converted to CBOR item:
[65536, -7, 1, ["text"]]
and finally to the binary string of:
0x841A000100002601816474657874
Appendix B. Implementation Guidance
When implementing text-form ARI decoding as a token lexer and LR(1)
parser, such as POSIX lex and yacc tools [IEEE.1003.1-2024], there
are some techniques that can avoid pitfalls.
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One is to use the generic val-seg rule from Section 4.1 as the
pattern to match any URI path segment. This requires multi-phase
processing in many cases, where the val-seg rule matches the segment
which is then percent-decoded and primitive or context-specific rules
are then used to decode the segment further. While the use of
percent encoding is discouraged when unnecessary, and for many ARI
values will be unnecessary, the generic URI syntax still allows for
percent encoding of segments and a robust ARI decoder needs to handle
that.
To avoid lexer ambiguities related to recursive ARI structures (which
are present in containers and parameters), it is best to combine the
entire object path of an Object Reference into a single token
consisting of slash-separated val-seg segments. When the lexer uses
capture length to perform tie-breaking between multiple rules that
match an input text this will cause the object path rule to be
preferred over Literal value rules (will which always contain fewer
path segments).
When handling literal values, the text encodings defined in this
document agree in many cases with text encodings provided by the C
language starting with C99 [ISO.9899-1999] for the following uses.
Signed Integer: This agrees with the printf() format %lld and the
parsing function strtoll(). Signed hexadecimals must be encoded
with the sign separately.
Unsigned Integer: This agrees with the printf() format %llu and
%llxand the parsing function strtoull().
Floating Point: This agrees with the printf() formats %e %f %g and
%a and the parsing function strtod(). This includes parsing of
non-finite values but encoders might need to handle those values
specially.
Decimal Fractions: These are used for TP and TD types. The sign,
integer portion, and fractional portion can each be handled as
separate components, with the latter two using unsigned integer
codecs (see above).
Absolute Times: This is used only for the TP type. The integer
portion is are compatible with the strftime() and strptime()
formats of %Y%m%dT%H%M%S, with the output having the "Z" zone
suffix appended and the input being stripped of optional "-" and
":" delimiters. The fractional portion can be handled the same as
for decimal fractions (above).
Relative Times: This is used only for the TD type. There is no
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direct handling of text form time duration but each separate
component can be handled as an unsigned decimal integer or decimal
fraction (see above).
Authors' Addresses
Edward J. Birrane, III
The Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Rd.
Laurel, MD 20723
United States of America
Phone: +1 443 778 7423
Email: Edward.Birrane@jhuapl.edu
Emery Annis
The Johns Hopkins University Applied Physics Laboratory
Email: Emery.Annis@jhuapl.edu
Brian Sipos
The Johns Hopkins University Applied Physics Laboratory
Email: brian.sipos+ietf@gmail.com
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