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(1) Store parameters required to make a protocol specific invocation to the thing, such as ___as <String Name="InterfacePort"/>
(2) Store information received from the thing, such as <Number Name="TempValue"/> (The TempValue from the temperature sensor)
(3) Hold fixed information about the thing, such as <String Name="Unit" default="Celsius"/>
(4) Act as control variables - variable that can activate certain actions
hold fixed information about the thing, such as the temperature unit
Action is where the processes to interact with things are defined.
The control variables in the ThingFacet are . They are called "actionable attributes". Actionable attributes are linked with one or more actions in the same ThingFacet by a modifier "KnownBy". For example: <Number Name="TempValue" KnownBy="SerialReadAction"/>
Action is where the processes to interact with things are defined.