SenML: Features and Versions
draft-bormann-core-senml-versions-00

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Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Updates: 8428 (if approved)                            February 10, 2020
Intended status: Standards Track
Expires: August 13, 2020

                      SenML: Features and Versions
                  draft-bormann-core-senml-versions-00

Abstract

   The Sensor Measurement Lists (SenML) specification provides a version
   number that is set to the number 10 in RFC 8428, without further
   specification on the way to make use of different version numbers.
   This short document specifies the use of "SenML Features" and maps
   them to SenML version numbers, updating RFC 8428.

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 August 13, 2020.

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

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Sensor Measurement Lists (SenML) specification [RFC8428] provides
   a version number that is 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
   "features" that can be added to the base version (version 10) in a
   fashion that is 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", 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 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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