SenML Data Value Content-Format Indication
draft-ietf-core-senml-data-ct-02
Network Working Group A. Keränen
Internet-Draft Ericsson
Intended status: Standards Track C. Bormann
Expires: 14 January 2021 Universität Bremen TZI
13 July 2020
SenML Data Value Content-Format Indication
draft-ietf-core-senml-data-ct-02
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.
Status of This Memo
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This Internet-Draft will expire on 14 January 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SenML Content-Format ("ct") Field . . . . . . . . . . . . . . 3
4. SenML Base Content-Format ("bct") Field . . . . . . . . . . . 4
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
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 interpret 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 interpretation 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 content-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].
{"n":"nfc-reader", "vd":"gmNmb28YKg", "ct":"60"}
Figure 2: SenML Record with binary data identified as CBOR
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In this example SenML Record the data value contains a string "foo"
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