In a UML system, the state machine associated with an object becomes active and ready to process events as soon as the object's initialization process is complete. Here's why:
Object Creation and State Machines: When an object is created, its associated state machine is instantiated along with it. This means the state machine's structural elements (states, transitions, etc.) are established.
Initialization and the Initial State: During the object's initialization phase, essential attributes and relationships might be set up, and the state machine enters its designated initial state.
Event Readiness: Once initialization is complete, the object and its state machine are considered "operational" and can respond to events as defined by the state machine's logic.
Why Other Options are Incorrect:
A. by the time the last state ends: State machines often don't have a designated "last" state. Their execution is based on events and can continue indefinitely. Additionally, a state machine can be ready to handle events long before ending.
B. immediately after the sequence diagrams start: Sequence diagrams illustrate interactions between objects, but they don't dictate the exact timing of object creation or state machine readiness in the overall system.
D. when all objects in the system are ready to receive events: While system-wide coordination might be necessary, an individual object's state machine readiness is dependent on its own initialization, not on the state of every other object.
References:
UML Specification (Superstructure) Version 2.5.1: Specifically, sections covering state machines (https://www.omg.org/spec/UML/2.5.1 ).
Practical guides to UML and object-oriented modeling often discuss object creation and state machine lifecycles.
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