]> Cisco Systems

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Cisco Systems

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Ericsson

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Applications and Real-Time A Semantic Definition Format for Data and Interactions of Things IoT This document defines protocol mapping extensions for the Semantic Definition Format (SDF) to enable mapping of protocol-agnostic SDF affordances to protocol-specific operations. The protocol mapping mechanism allows SDF models to specify how properties, actions, and events should be accessed using specific non-IP and IP protocols such as Bluetooth Low Energy, Zigbee or HTTP and CoAP. This document also describes a method to extend SCIM with an SDF model mapping. About This Document Status information for this document may be found at . Discussion of this document takes place on the A Semantic Definition Format for Data and Interactions of Things Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction

Protocol Mapping The Semantic Definition Format (SDF) provides a protocol-agnostic way to describe IoT devices and their capabilities through properties, actions, and events (collectively called affordances). When implementing the SDF model for a device on an actual implementation using specific communication protocols, there needs to be a mechanism to map the protocol-agnostic SDF definitions to protocol-specific operations, translating the model into a real-world implementation. This document defines such a mechanism using the sdfProtocolMap keyword, which allows SDF models to include protocol-specific mapping information attached to the protocol-agnostic definitions. An sdfProtocolMap can be applied to an sdfAffordance, be it an sdfProperty, sdfEvent or sdfAction. The mapping enables use cases such as application gateways or multi-protocol gateways that translate between different IoT protocols, automated generation of protocol-specific implementations from SDF models, and interoperability across heterogeneous device ecosystems. The protocol mapping mechanism is designed to be extensible: target protocols include non-IP protocols commonly used in IoT environments, such as and , as well as IP-based protocols such as HTTP or CoAP . This document registers mappings for BLE and Zigbee; future specifications can define mappings for additional protocols.

SCIM SDF model extension SDF provides a way to describe a class of devices and SCIM describes a device instance. The SDF model extension in this document defines a SCIM extension that enables inclusion of the SDF model for the class of devices a device belongs to in the SCIM object for that device.

Conventions and Definitions 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.

Structure This section defines the structure of an sdfProtocolMap. Because each protocol has its own addressing model, a single SDF affordance requires a distinct mapping per protocol. For example, BLE addresses a property as a service characteristic, while Zigbee addresses it as an attribute in a cluster of an endpoint. A protocol mapping object is a JSON object identified by the sdfProtocolMap keyword, nested inside an SDF affordance definition (sdfProperty, sdfAction, or sdfEvent). Protocol-specific attributes are embedded within this object, keyed by an IANA registered protocol name, e.g., "ble" or "zigbee".

Protocol Mapping Structure sdfProtocolMap | +-----> ble | | | +--> BLE-specific mapping | +-----> zigbee | | | +--> Zigbee-specific mapping | +-----> ... ]]>

SDF Extension Points The sdfProtocolMap keyword is introduced into SDF affordance definitions through the extension points defined in the formal syntax of (Appendix A). For each affordance type, an sdfProtocolMap entry is added via the corresponding CDDL group socket. The contents of the sdfProtocolMap object are in turn extensible through a protocol-mapping-specific group socket. A protocol MAY choose to extend only the affordance types that are applicable to it. For example, the BLE protocol mapping defines extensions for properties and events but not for actions.

Property Extension The $$SDF-EXTENSION-PROPERTY group socket in the propertyqualities rule of (Appendix A) is used to add protocol mapping to sdfProperty definitions:

SDF Property Extension Point for Protocol Mapping = ( name => props / { read: props, write: props } ) ]]>

The property-protocol-map generic () captures the common structure of property protocol mappings. The name parameter is the registered protocol name and props is the protocol-specific map of attributes. A protocol can provide either:

• A single mapping that applies to both read and write operations, or
• Separate read and write mappings when the protocol uses different attributes for each direction.

To extend $$SDF-PROPERTY-PROTOCOL-MAP for a new protocol (e.g., "new-protocol"), use the property-protocol-map generic with the protocol name and a map type defining the protocol-specific attributes. The protocol name ("new-protocol") MUST be registered in the IANA registry defined in . For example:

Example Property Protocol Map Extension ) new-protocol-property = { attributeA: text, attributeB: uint } ]]>

The corresponding JSON in an SDF model looks like:

Example Property Protocol Map in JSON

When a property uses different protocol attributes for read and write operations, the mapping can be split:

Example Property Protocol Map with Read/Write in JSON

Action Extension The $$SDF-EXTENSION-ACTION group socket in the actionqualities rule of (Appendix A) is used to add protocol mapping to sdfAction definitions:

SDF Action Extension Point for Protocol Mapping

Actions use a simpler structure than properties, as they do not require the read/write distinction. To extend $$SDF-ACTION-PROTOCOL-MAP for a new protocol, add a group entry mapping the protocol name to the protocol-specific attributes:

Example Action Protocol Map Extension

The corresponding JSON in an SDF model would look like:

Example Action Protocol Map in JSON

Event Extension The $$SDF-EXTENSION-EVENT group socket in the eventqualities rule of (Appendix A) is used to add protocol mapping to sdfEvent definitions:

SDF Event Extension Point for Protocol Mapping

Events follow the same simple pattern as actions. To extend $$SDF-EVENT-PROTOCOL-MAP for a new protocol:

Example Event Protocol Map Extension

The corresponding JSON in an SDF model looks like:

Example Event Protocol Map in JSON

Protocol Registration Protocol names used as keys in the sdfProtocolMap object (e.g., "ble", "zigbee") MUST be registered in the IANA registry defined in . A new protocol mapping MUST be defined by a specification that includes:

• A CDDL definition that extends at least one of the group sockets defined in this document: $$SDF-PROPERTY-PROTOCOL-MAP (), $$SDF-ACTION-PROTOCOL-MAP (), or $$SDF-EVENT-PROTOCOL-MAP (). Property mappings SHOULD use the property-protocol-map generic () to ensure a consistent structure.
• A description of the protocol-specific attributes introduced by the CDDL extension, including their semantics and how they relate to the underlying protocol operations.

Registered Protocol Mappings This section defines the protocol mappings registered by this document.

BLE The BLE protocol mapping allows SDF models to specify how properties and events should be accessed using Bluetooth Low Energy (BLE) protocol. The mapping includes details such as service IDs and characteristic IDs that are used to access the corresponding SDF affordances.

Properties For SDF properties, the BLE protocol mapping structure is defined as follows:

CDDL definition for BLE Protocol Mapping for properties ) ble-property = { serviceID: text, characteristicID: text } ]]>

Where:

• serviceID is the BLE service ID that corresponds to the SDF property.
• characteristicID is the BLE characteristic ID that corresponds to the SDF property.

For example, a BLE protocol mapping for a temperature property: For a temperature property that has different mappings for read and write operations, here is an example of the BLE protocol mapping:

Events For SDF events, the BLE protocol mapping structure is similar to SDF properties, but it must include additional attributes such as the type of the event.

BLE Protocol Mapping for events

Where:

• type specifies the type of BLE event, such as "gatt" for GATT events, "advertisements" for advertisement events, or "connection_events" for connection-related events.
• serviceID and characteristicID are optional attributes that are specified if the type is "gatt".

For example, a BLE event mapping for a heart rate measurement event: Here is an example of an isPresent event using BLE advertisements:

Zigbee The Zigbee protocol mapping allows SDF models to specify how properties, actions, and events should be accessed using the Zigbee protocol. The mapping includes details such as cluster IDs and attribute IDs that are used to access the corresponding SDF affordances.

Properties SDF properties are mapped to Zigbee cluster attributes. The Zigbee property protocol mapping structure is defined as follows:

CDDL definition for Zigbee Protocol Mapping for properties ) zigbee-property = { endpointID: uint, ? manufacturerCode: uint, clusterID: uint, attributeID: uint, attributeType: uint } ]]>

Where:

• endpointID is the Zigbee endpoint ID that corresponds to the SDF property.
• clusterID is the Zigbee cluster ID that corresponds to the SDF property.
• attributeID is the Zigbee attribute ID that corresponds to the SDF property.
• attributeType is the Zigbee data type of the attribute.
• manufacturerCode is the Zigbee manufacturer code of the attribute (optional).

For example, a Zigbee protocol mapping for a temperature property:

Events SDF events are mapped to Zigbee cluster attribute reporting. The Zigbee event protocol mapping structure is defined as follows:

CDDL definition for Zigbee Protocol Mapping for events

For example, a Zigbee event mapping for a temperature change report:

Actions SDF actions are mapped to Zigbee cluster commands. The Zigbee protocol mapping structure for actions is defined as follows:

CDDL definition for Zigbee Protocol Mapping for actions

Where:

• endpointID is the Zigbee endpoint ID that corresponds to the SDF action.
• clusterID is the Zigbee cluster ID that corresponds to the SDF action.
• commandID is the Zigbee command ID that corresponds to the SDF action.

For example, a Zigbee protocol mapping to set a temperature:

SCIM SDF Extension While SDF provides a way to describe a device class and SCIM defines a device instance, a method is needed to associate a mapping between an instance of a device and its associated SDF models. To accomplish this, we define a SCIM extension that can be used in conjunction with in . Implementation of this SCIM extension is OPTIONAL and independent of the protocol mapping functionality defined in the rest of this document. The SCIM schema attributes used here are described in Section 7 of .

SCIM SDF Extension Schema

Here is an example SCIM device schema extension with SDF models: An SDF model must be referenced with the sdf keyword inside the SCIM device schema as described in .

Security Considerations The security considerations of apply to this document as well. Each protocol mapped using this mechanism has its own security model. The protocol mapping mechanism defined in this document does not provide additional security beyond what is offered by the underlying protocols. Implementations MUST ensure that appropriate protocol-level security mechanisms are employed when accessing affordances through the mapped protocol operations.

IANA Considerations This section provides guidance to the Internet Assigned Numbers Authority (IANA) regarding registration of values related to this document, in accordance with .

Protocol Mapping IANA is requested to create a new registry called "SDF Protocol Mapping". The registration policy for this registry is "Specification Required" as defined in Section 4.6 of . The registry must contain the following attributes:

• Protocol map name
• Protocol name
• Description
• Reference of the specification describing the protocol mapping.

The specification requirements for a registration request are defined in . The designated expert(s) SHOULD verify that the protocol map name is appropriate and not likely to cause confusion with existing entries. The registrant of an existing entry may request updates to that entry, subject to the same expert review. They should verify that updates preserve backward compatibility with deployed implementations, or if breaking changes are necessary, consider whether a new registry entry is more appropriate. The following protocol mappings are described in this document: Protocol Mapping Registry

Protocol map	Protocol Name	Description	Reference
ble	Bluetooth Low Energy (BLE)	Protocol mapping for BLE devices	This document
zigbee	Zigbee	Protocol mapping for Zigbee devices	This document

SCIM Device Schema SDF Extension IANA is requested to create the following extensions in the SCIM Server-Related Schema URIs registry as described in :

URN	Description	Resource Type	Reference
urn:ietf:params:scim: schemas:extension: sdf:2.0:Device	SDF Extension	Device	This memo,

References Normative References 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. The Semantic Definition Format (SDF) is a format for domain experts to use in the creation and maintenance of data and interaction models that describe Things, i.e., physical objects that are available for interaction over a network. An SDF specification describes definitions of SDF Objects/SDF Things and their associated interactions (Events, Actions, and Properties), as well as the Data types for the information exchanged in those interactions. Tools convert this format to database formats and other serializations as needed. 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. North Carolina State University North Carolina State University Cisco Systems The initial core schema for SCIM (System for Cross-domain Identity Management) was designed for provisioning users. This memo specifies schema extensions that enables provisioning of devices, using various underlying bootstrapping systems, such as Wi-fi Easy Connect, FIDO device onboarding vouchers, BLE passcodes, and MAC authenticated bypass. The System for Cross-domain Identity Management (SCIM) specifications are designed to make identity management in cloud-based applications and services easier. The specification suite builds upon experience with existing schemas and deployments, placing specific emphasis on simplicity of development and integration, while applying existing authentication, authorization, and privacy models. Its intent is to reduce the cost and complexity of user management operations by providing a common user schema and extension model as well as binding documents to provide patterns for exchanging this schema using HTTP. This document provides a platform-neutral schema and extension model for representing users and groups and other resource types in JSON format. This schema is intended for exchange and use with cloud service providers. Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. Informative References Bluetooth SIG CSA IoT The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation. CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments.

CDDL Definition This appendix contains the combined CDDL definitions for the SDF protocol mappings. file "sdf-protocol-map.cddl" $$SDF-EXTENSION-PROPERTY //= ( sdfProtocolMap: { * $$SDF-PROPERTY-PROTOCOL-MAP } ) property-protocol-map = ( name => props / { read: props, write: props } ) $$SDF-EXTENSION-ACTION //= ( sdfProtocolMap: { * $$SDF-ACTION-PROTOCOL-MAP } ) $$SDF-EXTENSION-EVENT //= ( sdfProtocolMap: { * $$SDF-EVENT-PROTOCOL-MAP } ) $$SDF-PROPERTY-PROTOCOL-MAP //= ( property-protocol-map<"ble", ble-property> ) ble-property = { serviceID: text, characteristicID: text } $$SDF-EVENT-PROTOCOL-MAP //= ( ble: ble-event-map ) ble-event-map = { type: "gatt" / "advertisements" / "connection_events", ? serviceID: text, ? characteristicID: text } $$SDF-PROPERTY-PROTOCOL-MAP //= ( property-protocol-map<"zigbee", zigbee-property> ) zigbee-property = { endpointID: uint, ? manufacturerCode: uint, clusterID: uint, attributeID: uint, attributeType: uint } $$SDF-EVENT-PROTOCOL-MAP //= ( zigbee: zigbee-event-map ) zigbee-event-map = { endpointID: uint, ? manufacturerCode: uint, clusterID: uint, attributeID: uint, attributeType: uint } $$SDF-ACTION-PROTOCOL-MAP //= ( zigbee: zigbee-action-map ) zigbee-action-map = { endpointID: uint, ? manufacturerCode: uint, clusterID: uint, commandID: uint } ]]>

OpenAPI Definition The following non-normative model is provided for convenience of the implementor.

Protocol map for BLE

Protocol map for Zigbee

Acknowledgements This document relies on SDF models described in , as such, we are grateful to the authors of this document for putting their time and effort into defining SDF in depth, allowing us to make use of it. The authors would also like to thank the ASDF working group for their excellent feedback and steering of the document.