SenML Features and Versions
draft-ietf-core-senml-versions-00

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Last updated 2020-05-13
Replaces draft-bormann-core-senml-versions
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Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Updates: 8428 (if approved)                                  13 May 2020
Intended status: Standards Track                                        
Expires: 14 November 2020

                      SenML Features and Versions
                   draft-ietf-core-senml-versions-00

Abstract

   This short document updates RFC 8428, Sensor Measurement Lists
   (SenML), by specifying the use of independently selectable "SenML
   Features" and mapping them to SenML version numbers.

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
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   This Internet-Draft will expire on 14 November 2020.

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

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Feature Codes and the Version number  . . . . . . . . . . . .   2
   3.  Features: Reserved0, Reserved1, Reserved2, Reserved3  . . . .   3
   4.  Feature: Secondary Units  . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Sensor Measurement Lists (SenML) specification [RFC8428] provides
   a version number that is initially set to 10, without further
   specification on the way to make use of different version numbers.

   The traditional idea of using a version number for evolving an
   interchange format presupposes a linear progression of that format.
   A more likely form of evolution of SenML is the addition of
   independently selectable "features" that can be added to the base
   version (version 10) in a fashion that these are mostly independent
   of each other.  A recipient of a SenML pack can check the features it
   implements against those required by the pack, processing the pack
   only if all required features are provided in the implementation.

   This short document specifies the use of SenML Features and maps them
   to SenML version number space, updating [RFC8428].

   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.

   Where bit arithmetic is explained, this document uses the notation
   familiar from the programming language C, except that "**" denotes
   exponentiation.

2.  Feature Codes and the Version number

   The present specification defines "SenML Features", each identified
   by a "feature name" (a text string) and a "feature code", an unsigned
   integer less than 53.

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   The specific version of a SenML pack is composed of a set of
   features.  The SenML version number ("bver" field) is then a bitmap
   of these features, specifically the sum of, for each feature present,
   two taken to the power of the feature code of that feature.

               \~~   52                   fc
   version  =   >          present(fc) x 2
               /__ fc=0
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