SenML Data Value Content-Format Indication
draft-ietf-core-senml-data-ct-00
Network Working Group A. Keranen
Internet-Draft Ericsson
Intended status: Standards Track C. Bormann
Expires: March 1, 2020 Universitaet Bremen TZI
August 29, 2019
SenML Data Value Content-Format Indication
draft-ietf-core-senml-data-ct-00
Abstract
The Sensor Measurement Lists (SenML) media type supports multiple
types of values, from numbers to text strings and arbitrary binary
data values. In order to simplify processing of the data values this
document proposes to specify a new SenML field for indicating the
Content-Format of the data.
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Internet-Draft SenML Data Value Content-Format Indication August 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SenML Content-Format ("ct") Field . . . . . . . . . . . . . . 3
4. Using Content-Type and Content-Coding With the "ct" Field . . 3
5. SenML Base Content-Format ("bct") Field . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The Sensor Measurement Lists (SenML) media type [RFC8428] can be used
to send various different kinds of data. In the example given in
Figure 1, a temperature value, an indication whether a lock is open,
and a data value (with SenML field "vd") read from an NFC reader is
sent in a single SenML pack.
[
{"bn":"urn:dev:ow:10e2073a01080063:","n":"temp","u":"Cel","v":7.1},
{"n":"open","vb":false},
{"n":"nfc-reader","vd":"aGkgCg"}
]
Figure 1: SenML pack with unidentified binary data
The receiver is expected to know how to decode the data in the "vd"
field based on the context, e.g., name of the data source and out-of-
band knowledge of the application. However, this context may not
always be easily available to entities processing the SenML pack. To
facilitate automatic decoding it is useful to be able to indicate an
Internet media type and content-coding right in the SenML Record.
The CoAP Content-Format (Section 12.3 in [RFC7252]) provides just
this information; enclosing a Content-Format number (in this case
number 60 as defined for media type application/cbor in [RFC7049]) in
the Record is illustrated in Figure 2. All registered CoAP content
formats are listed in the Content Formats subregistry of the CoRE
Parameters registry [IANA.core-parameters].
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{"n":"nfc-reader", "vd":"gmNmb28YKg", "ct":60}
Figure 2: SenML Record with binary data identified as CBOR
In this example SenML Record the data value contains a string "foo"
and a number 42 encoded in a CBOR [RFC7049] array. Since the example
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