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Network Working Group                                         A. Keranen
Internet-Draft                                                  Ericsson
Intended status: Standards Track                              M. Mohajer
Expires: January 4, 2019                                       u-blox UK
                                                            July 3, 2018


          FETCH & PATCH with Sensor Measurement Lists (SenML)
                   draft-keranen-core-senml-fetch-01

Abstract

   The Sensor Measurement Lists (SenML) media type and data model can be
   used to send collections of resources, such as batches of sensor data
   or configuration parameters.  The CoAP iPATCH, PATCH, and FETCH
   methods enable accessing and updating parts of a resource or multiple
   resources with one request.  This document defines semantics for the
   CoAP iPATCH, and FETCH methods for resources represented with the
   SenML data model.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 4, 2019.

Copyright Notice

   Copyright (c) 2018 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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   (http://trustee.ietf.org/license-info) in effect on the date of
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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Using FETCH and iPATCH with SenML . . . . . . . . . . . . . .   3
     3.1.  SenML FETCH . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  SenML iPATCH  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Sensor Measurement Lists (SenML) media type [I-D.ietf-core-senml]
   and data model can be used to transmit collections of resources, such
   as batches of sensor data or configuration parameters.

   Example of a SenML collection is shown below:

   [
    {"bn":"2001:db8::2/3306/0/", "n":"5850", "vb":true},
    {"n":"5851", "v":42},
    {"n":"5750", "vs":"Ceiling light"}
   ]

   Here three resources "3306/0/5850", "3306/0/5851", and "3306/0/5750",
   of an IPSO dimmable light smart object [IPSO] are represented using a
   single SenML Pack with three SenML Records.  All resources share the
   same base name "2001:db8::2/3306/0/", hence full names for resources
   are "2001:db8::2/3306/0/5850", etc.

   The CoAP [RFC7252] iPATCH and FETCH methods [RFC8132] enable
   accessing and updating parts of a resource or multiple resources with
   one request.

   This document defines semantics for the CoAP iPATCH and FETCH methods
   for resources represented with the SenML data model.  Same semantics
   apply also for the CoAP PATCH method.






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2.  Terminology

   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.

   Readers should also be familiar with the terms and concepts discussed
   in [RFC8132] and [I-D.ietf-core-senml].  Also the following terms are
   used in this document:

   FETCH Record:  One set of parameters that is used to match SenML
      Record(s).

   FETCH Pack:  One or more FETCH Records in an array structure.
      Presented using the SenML media type.

   PATCH Record:  One set of parameters similar to FETCH Record but
      contains also instructions on how to change existing SenML
      Pack(s).

   PATCH Pack:  One or more PATCH Records in an array structure.

3.  Using FETCH and iPATCH with SenML

   The FETCH and iPATCH methods use the same SenML media type to enable
   re-use of existing SenML parsers and generators, in particular on
   constrained devices.

3.1.  SenML FETCH

   The FETCH method can be used to select and return parts of one or
   more SenML Packs.  The SenML Records are selected by giving the
   name(s) of the resources using the SenML "name" and/or "base name"
   Fields.

   For example, to select resources "5850" and "5851" from the example
   in Section 1, the following FETCH Pack can be used:

   [
    {"bn":"2001:db8::2/3306/0/", "n":"5850"},
    {"n":"5851"}
   ]

   The result to a FETCH request with the example above would be:





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   [
    {"bn":"2001:db8::2/3306/0/", "n":"5850", "vb":true},
    {"n":"5851", "v":42},
   ]

   When SenML Records contain also time values, a name may no longer
   uniquely identify a single Record.  When no time is given in a FETCH
   Record, all SenML Records with the given name are be matched.  When
   time is given in the FETCH Record, only a SenML Record (if any) with
   equal time value and name is matched.

3.2.  SenML iPATCH

   The iPATCH method can be used to change the values of SenML Records,
   to add new Records, and to remove existing Records.  The names and
   times of the PATCH Records are given and matched in same way as for
   the FETCH method but PATCH Packs can include also new values and
   other SenML Fields for the Records.

   When the name, or time and name, in a PATCH Record matches with an
   existing Record, the Record is replaced with the contents of the
   PATCH Record.

   If a PATCH Record contains a combination of a time value and a name
   that do not exist in any existing Record in the Pack, the given
   Record, with all the fields it contains, is added to the Pack.

   If a PATCH Record has a value field with value null, the matched
   Records (if any) are removed from the Pack.

   For example, the following document could be given as iPATCH payload
   to change/set values of two SenML Records for the example in
   Section 1:

   [
    {"bn":"2001:db8::2/3306/0/", "n":"5850", "vb":false},
    {"n":"5851", "v":10}
   ]

   If the request is successful, the resulting representation of the
   example SenML Pack would be as follows:

   [
    {"bn":"2001:db8::2/3306/0/", "n":"5850", "vb":false},
    {"n":"5851", "v":10},
    {"n":"5750", "vs":"Ceiling light"}
   ]




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4.  Security Considerations

   The security and privacy considerations of SenML apply also with the
   FETCH and iPATCH methods.

   Since the the FETCH and iPATCH methods potentially allow retrieving
   or changing many resources at once, particular care must be taken to
   ensure that access control rules for different resources are
   respected.

5.  Acknowledgements

   The use of FETCH and iPATCH methods with SenML was first introduced
   by the OMA SpecWorks LwM2M v1.1 specification.  This document
   generalizes the use to any SenML representation.  The authors would
   like to thank Jaime Jimenez, Klaus Hartke, and also everyone in the
   IETF CoRE and OMA SpecWorks DMSE working groups for their
   contributions and reviews.

6.  References

6.1.  Normative References

   [I-D.ietf-core-senml]
              Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Sensor Measurement Lists (SenML)", draft-ietf-
              core-senml-16 (work in progress), May 2018.

   [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>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252, DOI 10.17487/
              RFC7252, June 2014, <https://www.rfc-editor.org/info/
              rfc7252>.

   [RFC8132]  van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
              FETCH Methods for the Constrained Application Protocol
              (CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
              <https://www.rfc-editor.org/info/rfc8132>.

   [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>.





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6.2.  Informative References

   [IPSO]     IPSO, "IP for Smart Objects - IPSO Objects", 2018,
              <https://github.com/IPSO-Alliance/pub>.

Authors' Addresses

   Ari Keranen
   Ericsson

   Email: ari.keranen@ericsson.com


   Mojan Mohajer
   u-blox UK

   Email: Mojan.Mohajer@u-blox.com


































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