LM12-TEXT (CH 13)

State

a mode or condition of being

T/F: States must be discernible from one another, so an entity with several states must have varying characteristics that identify its states.

True

T/F: Transitions may be constrained to occur only under certain circumstances

True

T/F:Transitions may also themselves give rise to events.

True

What must a finite automation spec contain?

• Distinguishable descriptions of the automaton's states

• Descriptions of transitions indicating each transition's source state, target state, and the events that trigger it

• Designation of initial state, the starting place for state transitions.

Finite Automata:

model some entity's state-based behavior

deterministic finite automaton

A finite automaton that has no spontaneous transitions and has a single transition that it must make in response to every event in each of its states.

A non-deterministic finite automaton

A finite automation that is not deterministic.

How are finite automata useful?

Help analyze, design, specify, and document the behavior of computational entities

UML State Diagram

Notation for specifying finite automata

State Symbol Compartments:

3 Compartments: name, internal transitions, nested diagram

Two types of composite states:

Sequential, Concurrent

Sequential Composite State

contains a single state diagram composed of sub- states or inner states and the transitions between them.

Concurrent Composite State

contains two or more sequential state diagrams in regions separated by dashed lines called concurrent region boundary lines.

T/F: A sequential composite state includes a nested state diagram that decomposes the composite state.

True

How do sequential composite states simplify state models?

• Organize states into hierarchies.

• Consolidate many transitions.

What do advanced UML State Diagrams depict?

Concurrent Composite States

How are transitions into a concurrent composite state made?

• Through the composite state boundary.

• Directly through one of the sub-states.

How are transitions from a concurrent composite state made?

• By a non-completion event that causes all sub-states to be exited.

• By a completion event in which one sub-state transition to external state causes exit from other concurrent states.

How are concurrent composite states helpful in simplifying state diagrams?

Greatly reducing the number of states and transitions.

History State:

A pseudo-state that serves as a marker indicating that the sub-state last active when the composite state was exited should be reentered.