[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 draft-ietf-core-senml-etch

Network Working Group                                         A. Keranen
Internet-Draft                                                  Ericsson
Intended status: Standards Track                              M. Mohajer
Expires: April 25, 2019                                        u-blox UK
                                                        October 22, 2018


          FETCH & PATCH with Sensor Measurement Lists (SenML)
                   draft-keranen-core-senml-fetch-03

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
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 25, 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
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



Keranen & Mohajer        Expires April 25, 2019                 [Page 1]


Internet-Draft          FETCH & PATCH with SenML            October 2018


   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 {{RFC8428} 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.






Keranen & Mohajer        Expires April 25, 2019                 [Page 2]


Internet-Draft          FETCH & PATCH with SenML            October 2018


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 [RFC8428].  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 also
      containing instructions on how to change existing SenML Pack(s).

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

   Target Record:  A Record in a SenML Pack that is matching the
      selection criteria of a Fetch or Patch Record and hence is a
      target for a Fetch or Patch operation.

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.

   NOTE: it is currently under consideration whether new media types
   should be registered for FETCH/iPATCH instead of re-using the SenML
   media types.

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:





Keranen & Mohajer        Expires April 25, 2019                 [Page 3]


Internet-Draft          FETCH & PATCH with SenML            October 2018


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

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

   [
    {"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 matched.  When time
   is given in the Fetch Record, only a SenML Record (if any) with equal
   time value and name is matched.

   The resolved form of records (Section 4.6 of [RFC8428]) is used when
   comparing the names and times of the Target and Fetch Records to
   accommodate for differences in use of the base values.

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 Records, except each Patch Record can match at most one
   Target Record.  Patch Packs can also include new values and other
   SenML Fields for the Records.

   When the name in a Patch Record matches with the name in an existing
   Record, the time values are compared.  If the time values do not
   exist or are equal in both Records, the Target Record is replaced
   with the contents of the Patch Record.

   If a Patch Record contains a name, or 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
   Record (if any) is 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:





Keranen & Mohajer        Expires April 25, 2019                 [Page 4]


Internet-Draft          FETCH & PATCH with SenML            October 2018


   [
    {"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"}
   ]

4.  Security Considerations

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

   In FETCH and iPATCH requests, the client can pass arbitrary names to
   the target resource for manipulation.  The resource implementer must
   take care to only allow access to names that are actually part of (or
   accessible through) the target resource.

   If the client is not allowed to do a GET or PUT on the full target
   resource (and thus all the names accessible through it), access
   control rules must be evaluated for each record in the pack.

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 Carsten Bormann, Christian Amsuess, 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

   [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>.






Keranen & Mohajer        Expires April 25, 2019                 [Page 5]


Internet-Draft          FETCH & PATCH with SenML            October 2018


   [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>.

   [RFC8428]  Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
              DOI 10.17487/RFC8428, August 2018,
              <https://www.rfc-editor.org/info/rfc8428>.

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















Keranen & Mohajer        Expires April 25, 2019                 [Page 6]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/