]> Universität Bremen TZI

Postfach 330440 Bremen D-28359 Germany +49-421-218-63921 cabo@tzi.org

Universität Bremen

jan.romann@uni-bremen.de

Applications ASDF Internet-Draft The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things. It was created as a common language for use in the development of the One Data Model liaison organization (OneDM) definitions. Tools convert this format to database formats and other serializations as needed. An SDF specification often needs to be augmented by additional information that is specific to its use in a particular ecosystem or application. SDF mapping files provide a mechanism to represent this augmentation. Discussion Venues Discussion of this document takes place on the asdf Working Group mailing list (asdf@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things. It was created as a common language for use in the development of the One Data Model liaison organization (OneDM) definitions. Tools convert this format to database formats and other serializations as needed. An SDF specification often needs to be augmented by additional information that is specific to its use in a particular ecosystem or application. SDF mapping files provide a mechanism to represent this augmentation.

Terminology and Conventions The definitions of apply. The term "byte" is used in its now-customary sense as a synonym for "octet". 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 when, and only when, they appear in all capitals, as shown here.

Overview An SDF mapping file provides augmentation information for one or more SDF definitions. Its main contents is a map from SDF name references () to a set of qualities. When processing the mapping file together with one or more SDF definitions, these qualities are added to the SDF definition at the referenced name, as in a merge-patch operation . Note that this is somewhat similar to the way sdfRef () works, but in a mapping file the arrows point in the inverse direction (from the augmenter to the augmented).

Example Definition 1 (ecosystem: IPSO/OMA) An example for an SDF mapping file is given in . This mapping file is meant to attach to an SDF specification published by OneDM, and to add qualities relevant to the IPSO/OMA ecosystem.
Note that this example uses namespaces to identify elements of the referenced specification(s), but has un-namespaced quality names. These two kinds of namespaces are probably unrelated, and we may need to add quality namespacing to SDF (independent of a potential feature to add namespace references to definitions that are not intended to go into the default namespace -- these are SDF definition namespaces and not quality namespaces, which are one meta-level higher).

• Start of mapping file for certain OneDM playground models:

A simple example of an SDF mapping file

Example Definition 2 (ecosystem: W3C WoT) This example shows a the translation of a hypothetical W3C WoT Thing Model into an SDF model plus a mapping file to catch Thing Model attributes that don't currently have SDF qualities defined.
The example probably would be more useful with, say, protocol bindings. This is left for a future version of this example, and/or a future specification that specifically addresses how to map Thing Models into SDF.
(There is also the separate requirement to transform a Thing Description into the kind of information that can be represented in SDF plus instance information, such as IP addresses or specific node names.)
Finally, namespaces are all wrong in this example.

• The input: WoT Thing Model

Input: WoT Thing Model

• The output: SDF model

Output 1: SDF Model

• The other output: SDF mapping file

Output 2: SDF Mapping File

Formal Syntax of SDF mapping files An SDF mapping file has three optional components that are taken unchanged from SDF: The info block, the namespace declaration, and the default namespace. The mandatory fourth component, the "map", contains the mappings from a SDF name reference (usually a namespace and a JSON pointer) to a nested map providing a set of qualities to be merged in at the site identified in the name reference. describes the syntax of SDF mapping files using CDDL .

CDDL definition of SDF mapping file ? defaultNamespace: text ? map: { * sdf-pointer => additionalqualities} } ; we can't really be much more specific here: additionalqualities = named ; --------------------------------- import from SDF: sdfinfo = { ? title: text ? version: text ? copyright: text ? license: text EXTENSION-POINT<"info-ext"> } ; Shortcut for a map that gives names to instances of X (has text keys and values of type X) named = { * text => X } EXTENSION-POINT = ( * (text .feature f) => any ) ; only used in framework syntax sdf-pointer = text ; .regexp curie-regexp -- TO DO! ]]>

IANA Considerations

Media Type IANA is requested to add the following Media-Type to the "Media Types" registry. A media type for SDF mapping files

Name	Template	Reference
sdf-mapping+json	application/sdf-mapping+json	RFC XXXX,

RFC Editor: please replace RFC XXXX with this RFC number and remove this note.

Type name:

application

Subtype name:

sdf-mapping+json

Required parameters:

none

Optional parameters:

none

Encoding considerations:

binary (JSON is UTF-8-encoded text)

Security considerations:

of RFC XXXX

Interoperability considerations:

none

Published specification:

of RFC XXXX

Applications that use this media type:

Tools for data and interaction modeling in the Internet of Things

Fragment identifier considerations:

A JSON Pointer fragment identifier may be used, as defined in .

Person & email address to contact for further information:

ASDF WG mailing list (asdf@ietf.org), or IETF Applications and Real-Time Area (art@ietf.org)

Intended usage:

COMMON

Restrictions on usage:

none

Author/Change controller:

IETF

Provisional registration:

no

Registries (TBD: After future additions, check if we need any.)

Security Considerations Some wider issues are discussed in . (Specifics: TBD.)

References Normative References JSON Pointer defines a string syntax for identifying a specific value within a JavaScript Object Notation (JSON) document. This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON. This specification defines the JSON merge patch format and processing rules. The merge patch format is primarily intended for use with the HTTP PATCH method as a means of describing a set of modifications to a target resource's content. PassiveLogic Universität Bremen TZI The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things. It was created as a common language for use in the development of the One Data Model liaison organization (OneDM) definitions. Tools convert this format to database formats and other serializations as needed. An SDF specification describes definitions of SDF Objects and their associated interactions (Events, Actions, Properties), as well as the Data types for the information exchanged in those interactions. // A JSON format representation of SDF 1.0 was defined in version // (-00) of this document; version (-05) was designated as an // _implementation draft_, labeled SDF 1.1, at the IETF110 meeting of // the ASDF WG (2021-03-11). The present version (-08) adds URIs as // alternative measurement unit names, is editorially more self- // contained, and uses updated xml2rfc conventions for its plain-text // rendering. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References The Internet of Things (IoT) concept refers to the usage of standard Internet protocols to allow for human-to-thing and thing-to-thing communication. The security needs for IoT systems are well recognized, and many standardization steps to provide security have been taken -- for example, the specification of the Constrained Application Protocol (CoAP) secured with Datagram Transport Layer Security (DTLS). However, security challenges still exist, not only because there are some use cases that lack a suitable solution, but also because many IoT devices and systems have been designed and deployed with very limited security capabilities. In this document, we first discuss the various stages in the lifecycle of a thing. Next, we document the security threats to a thing and the challenges that one might face to protect against these threats. Lastly, we discuss the next steps needed to facilitate the deployment of secure IoT systems. This document can be used by implementers and authors of IoT specifications as a reference for details about security considerations while documenting their specific security challenges, threat models, and mitigations. This document is a product of the IRTF Thing-to-Thing Research Group (T2TRG).

Acknowledgements This draft is based on discussions in the Thing-to-Thing Research Group (T2TRG) and the SDF working group. Input for was provided by .