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ThingModel is one special kind of models (the other kinds are DataModels and AppModels). Therefore it has all the properties of Models (Lifecycle of models, Model Attributes, Unique and Constraints).

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However, as a recommended practice, the Attributes and Actions related to the interactions with an external thing (sensors, actuators, machines) are often defined in a reusable structure called ThingFacet, and combined into a ThingModel. This relationship was explained in the concept of Models and Model Facets.

ThingModel is a complex type defined by Atomic Domain Language Thing Definition Language (TDL). ThingModel inherits ThingFacet and a DataModel.

Here is the complete definition of a ThingModel:

<Def name="ThingModel" inherits="ThingFacet,DataModel" documentation="A complete model of a device or other kind of thing"/>

 Application related information are often defined directly as attributes of the ThingModel.

Purpose of ThingModels:

• ThingModels are normally defined by users when interacting with Physical Things. The behavior of Physical Things are modeled via ThingFacet.
• ThingModels are driver for ThingFacets. ThingFacet (s) are reusable models and TQL CRUD operations can not be performed on ThingFacet. ThingFacet(s) are put to use only when combined within a ThingModel.
• ThingModels can contain application related information that are related to things.

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<ThingModel Name="PhidgetServoModel">
  	<Sid Name="PhidServoId"/>
</ThingModel>
<ThingFacet Name="PhidgetServoFacet">
	<String Name="ServoProtocolURL" Default="phid://" />
	<String Name="DeviceInterfaceIndex" />
	<String Name="PhidgetDeviceType" />
	<Integer Name="ServoAngle" KnownBy="PhidgetServoAction" />
	<Action Name="PhidgetServoAction" Documentation="Control servo motor">
		...
	</Action>
</ThingFacet>

ThingsFacets are used within ThingModels using Combines modifier. Example of a PhidgetServoModel ThingModel combining a PhidgetServoFacet ThingFacet

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