SenML Data Value Content-Format Indication
draft-ietf-core-senml-data-ct-02

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Last updated 2020-07-30 (latest revision 2020-07-13)
Replaces draft-keranen-core-senml-data-ct
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Network Working Group                                         A. Keränen
Internet-Draft                                                  Ericsson
Intended status: Standards Track                              C. Bormann
Expires: 14 January 2021                          Universität Bremen TZI
                                                            13 July 2020

               SenML Data Value Content-Format Indication
                    draft-ietf-core-senml-data-ct-02

Abstract

   The Sensor Measurement Lists (SenML) media type supports multiple
   types of values, from numbers to text strings and arbitrary binary
   data values.  In order to simplify processing of the data values this
   document proposes to specify a new SenML field for indicating the
   Content-Format of the data.

Status of This Memo

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

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   This Internet-Draft will expire on 14 January 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   provided without warranty as described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SenML Content-Format ("ct") Field . . . . . . . . . . . . . .   3
   4.  SenML Base Content-Format ("bct") Field . . . . . . . . . . .   4
   5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Sensor Measurement Lists (SenML) media type [RFC8428] can be used
   to send various different kinds of data.  In the example given in
   Figure 1, a temperature value, an indication whether a lock is open,
   and a data value (with SenML field "vd") read from an NFC reader is
   sent in a single SenML pack.

   [
     {"bn":"urn:dev:ow:10e2073a01080063:","n":"temp","u":"Cel","v":7.1},
     {"n":"open","vb":false},
     {"n":"nfc-reader","vd":"aGkgCg"}
   ]

             Figure 1: SenML pack with unidentified binary data

   The receiver is expected to know how to interpret the data in the
   "vd" field based on the context, e.g., name of the data source and
   out-of-band knowledge of the application.  However, this context may
   not always be easily available to entities processing the SenML pack.
   To facilitate automatic interpretation it is useful to be able to
   indicate an Internet media type and content-coding right in the SenML
   Record.  The CoAP Content-Format (Section 12.3 in [RFC7252]) provides
   just this information; enclosing a Content-Format number (in this
   case number 60 as defined for content-type application/cbor in
   [RFC7049]) in the Record is illustrated in Figure 2.  All registered
   CoAP Content-Formats are listed in the Content-Formats subregistry of
   the CoRE Parameters registry [IANA.core-parameters].

   {"n":"nfc-reader", "vd":"gmNmb28YKg", "ct":"60"}

         Figure 2: SenML Record with binary data identified as CBOR

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   In this example SenML Record the data value contains a string "foo"
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