The W3C WoT Thing Description [[wot-thing-description11]] specification - defines a building block of the Web of Things, by specifying an - information model and JSON-based representation format for describing the - capabilities of connected devices and the interfaces with which to - communicate with them. + defines an information model and JSON-based representation format for + describing the capabilities of connected devices and the interfaces with + which to communicate with them. Thing Descriptions are designed to be + protocol-agnostic and flexible enough to describe a wide range of + existing ("brownfield") IoT devices.
- The Thing Description specification is designed to be protocol-agnostic - and flexible enough to describe a wide range of existing ("brownfield") - IoT devices, rather than specifying a fixed protocol or application - programming interface (API) which all devices must implement. The downside - of this open ended flexibility is that it makes ad-hoc interoperability on - the Web of Things very difficult, because it's nearly impossible to create - a single WoT Consumer [[wot-architecture]] - which is guaranteed to be able to communicate with any - Web Thing [[wot-architecture]] out of the box. + In order to provide this level of flexibility the Thing Description + specification includes a number of extension points including protocol + bindings, payload bindings, security mechanisms, link relations and + semantic contexts. As long as all of the capabilities of a device can + be described using a Thing Description and a + Consumer implements all of the extensions used, the Consumer should + be able to interoperate with that device. However, the result of this + extensible architecture is that any given Consumer can only interoperate + with a subset of possible Web Things.
This specification is designed to complement the Thing Description - [[wot-thing-description11]] specification, by defining a - Profiling Mechanism and a set of - Profiles which enable - out-of-the-box - interoperability between Web Things and their - Consumers. + [[wot-thing-description11]] specification, by enabling ad-hoc + interoperability through the use of "profiles". A profile + prescribes a finite set of extensions and defaults that a Thing can + be constrained to in order to guarantee + out-of-the-box + interoperability with any Consumer which implements that profile.
Profiles are designed specifically for new ("greenfield") implementations where developers have the freedom to conform to a prescriptive protocol binding and set of common constraints, in order to benefit from - out-of-the-box interoperability. + this additional level of interoperability.
Of the Profiles defined in this specification, only the