SenML Base Time Offset Attribute
draft-groves-core-senml-bto-00

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Last updated 2016-10-17
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CoRE Working Group                                             C. Groves
Internet-Draft                                                   W. Yang
Intended status: Standards Track                                  Huawei
Expires: April 20, 2017                                 October 17, 2016

                    SenML Base Time Offset Attribute
                     draft-groves-core-senml-bto-00

Abstract

   SenML [I-D.ietf-core-senml] defines a base time attribute and time
   value which is used to determine the time when a value is recorded.
   In some applications a SenML package will contain a series of records
   related to a constant sample time interval, e.g. once every 60
   seconds.  This means that the time attribute will be required for
   each record.  This document defines a new "time offset" base
   attribute that allows a sender to include the time for the sample
   interval between records.  If the "time offset" base attribute is
   used the sender will not send the time attribute for each record,
   minimising message and storage size.

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   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  SenML Structure and Semantics . . . . . . . . . . . . . . . .   4
     3.1.  Base Attributes . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Regular Attributes  . . . . . . . . . . . . . . . . . . .   4
     3.3.  Considerations  . . . . . . . . . . . . . . . . . . . . .   4
   4.  JSON Representation (application/senml+json)  . . . . . . . .   5
   5.  CBOR Representation (application/senml+cbor)  . . . . . . . .   5
   6.  XML representation (application/senml+xml)  . . . . . . . . .   5
   7.  EXI Representation (application/senml-exi)  . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   SenML currently defines the base time "bt" and time "t" attributes to
   indicate the time that each value in a SenML record is recorded.
   This means that for each record (value "v") that a "t" attribute is
   required.  The example from section 5.1.2/[I-D.ietf-core-senml] is
   copied below to illustrate a SenML package with multiple records.

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   [ {"bn": "urn:dev:ow:10e2073a01080063",
         "bt": 1320067464,
         "bu": "%RH",
         "v": 21.2, "t": 0 },
         { "v": 21.3, "t": 10 },
         { "v": 21.4, "t": 20 },
         { "v": 21.4, "t": 30 },
         { "v": 21.5, "t": 40 },
         { "v": 21.5, "t": 50 },
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