Introduction of the notion
Source: Semantic Aspect Guide; page 6
The semantic class carries properties that are informative, active or cooperative (structural) in nature.
They are translated in UML in the form of an attribute, if necessary, derived (and so created by a software operation).
They presuppose an action or a transformation of the object. They are written in UML, in the form of an operation. If the object is transformed by the action requested, the operation will be managed by a state machine.
They are the classification and association relations (including composition).
Informative, active or cooperative (structural) information that applies to each instance or all instances of a semantic class