A Semantic Definition Format for Data and Interactions of Things

Document Proposed charter A Semantic Definition Format for Data and Interactions of Things WG (asdf)
Title A Semantic Definition Format for Data and Interactions of Things
Last updated 2020-09-21
State External Review (Message to Community, Selected by Secretariat) Initial chartering
WG State Proposed
IESG Responsible AD Barry Leiba
Charter Edit AD Barry Leiba
Telechat date On agenda of 2020-10-08 IESG telechat
Send notices to (None)


## Background

Data and interaction models of IoT devices today exhibit unneeded diversity
between different industry ecosystem standards development organizations
(SDOs), hindering interoperability across these ecosystems with little
discernible benefit from the diversity. Early 2019, One Data Model (OneDM) was
started to bring several IoT SDOs and IoT device and platform vendors together
under a broad, multi-party liaison agreement, with a goal of arriving at a
common set of data and interaction models that describe IoT devices. Ideally,
for every class of IoT device, there is just a single model selected/created by
the participating organizations, which everyone can adopt.

As a common language for writing down these models, the Semantic Definition
Format (SDF) was created, which can represent IoT Things, their composition
from reusable Objects, their Interaction Affordances (Properties, Actions,
Events), and the data models relevant to describe these Affordances.  SDF
represents these models in JSON, enabling re-use of specification formats such
as CDDL (RFC8610) and the formats proposed at json-schema.org and their
tooling, for describing both the SDF format itself and the structure of the
data to be modelled in SDF.

Some 200 models in SDF format have been contributed by participating
ecosystems; new models are being submitted continually. Version 1.0 of the SDF
specification was published on the OneDM github repository and as an
Internet-Draft. OneDM is now focusing on consolidating the body of submitted
models and developing processes for arriving at harmonized models that span
different industry ecosystems in a common way; they look to the IETF for
developing SDF 1.0 further into a high-quality specification.

The IETF also defines the YANG data modelling language (RFC 7950). YANG has a
strong focus on modelling the management interface for network devices, using a
fairly small set of network management protocols, whereas SDF is designed to
span (and transitively unify) many existing interaction models already present.
While data associated with a YANG schema can be serialized to a variety of wire
formats (e.g., XML, JSON, CBOR, and others), the serialization is driven
directly by the structure of the data models defined in YANG; there is no
separate "protocol binding" step as in the use of SDF.

Conversely, SDF does not deal directly with serialization at all, modelling
only the structure and semantics of the data being interchanged, hence leaving
data serialization (and RPC semantics) to other standards, most likely defined
by existing IoT SDOs.

## The ASDF Working Group

The objective of the ASDF working group is to develop SDF to an
IETF-quality specification for Thing Interaction and Data Modelling,
working with experts from OneDM and its contributing organizations.  On
the way to that specification, further functionality requirements will be
addressed that emerge in the usage of SDF for model harmonization.

The ASDF WG will work closely with the CBOR WG, home of the CDDL
specification.  It will also engage the still active mailing list of the
concluded JSON WG.  Recent proposals to form an IRTF formal description
techniques (FDT) Research Group might lead to another collaboration
partner.  The Thing-to-Thing Research Group (T2TRG) and its WISHI program
can be instrumental in engaging researchers and other SDOs in this space,
such as W3C Web of Things, which is working on Thing Description
Templates and related specifications.

Proposed milestones

Proposed milestones

Date Milestone
1 Sep 2021 SDF specification, publication requested
1 Oct 2020 SDF specification, WG document adopted