Introduction à la modélisation orientée objets avec UML

class A class that cannot be directly instantiated. Contrast :concrete class. abstraction : The essential characteristics of an entity that distinguish it from all other kinds of entities. An abstraction defines a boundary relative to the perspective of the viewer. action : The specification of an executable statement that forms an abstraction of a computational procedure. An action typically results in a change in the state of the system, and can be realized by sending a message to an object or modifying a link or a value of an attribute. action sequence : An expression that resolves to a sequence of actions. action state : A state that represents the execution of an atomic action, typically the invocation of an operation. activation : The execution of an action. active class : A class whose instances are active objects. See : active object. active object : An object that owns a thread and can initiate control activity. An instance of active class. See : active class, thread.