PB007 Software Engineering I — Getting Dynamic, State Machine Diagram1
Getting Dynamic,
State Machine Diagram
PB007 Software Engineering I
Lukáš Daubner
daubner@mail.muni.cz
PB007 Software Engineering I — Getting Dynamic, State Machine Diagram2
State Machine Diagram
̶ Models the dynamic behavior (life cycle) of one subject
̶ Class instantiation (Object)
̶ Use Case
̶ System
̶ Subsystem
̶ Component
̶ …
̶ Main components are:
̶ States
̶ Transitions
̶ Events
State
Event
Transition
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States
State Machine Diagram
̶ Represents semantically important situation
̶ In case of (OOP) object, it is determined by attribute values,
relations with others, and performed activity.
Entry action
Performed when entering the state
Exit action
Performed when exiting the state
Internal activity
Ongoing behavior while
in the state
Deferrable Trigger
Event, which is registered but its
processing is left for other states
Internal Transition
Transition, which is processed
without exiting the sate
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Transitions
State Machine Diagram
̶ Defines how to get from one state to another
̶ Syntax: event [guard condition] / action
̶ Semantics: At the occurrence of event, if the guard condition
holds, perform action and go to the new state.
Event Condition (bool) Action
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Events
State Machine Diagram
̶ Stimulus on which the subject may react by changing the state or
performing an operation.
̶ Types of events:
̶ Call event – Calling operation of the subject.
̶ Signal event – Asynchronous sending a receiving a signal between subjects
̶ Change event – Boolean expression. The event occurs when the value is changed from
false to true.
̶ Time event – Event occur at a certain time t (when(t)) or after a certain time t (after(t)).
PB007 Software Engineering I — Getting Dynamic, State Machine Diagram6
Events
State Machine Diagram
(excerpt from diagram)
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Simple composite state
Composite States
̶ Useful for simplifying the diagram
̶ Capturing inheritance between states
̶ Consist of a single region
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Orthogonal composite state
Composite States
̶ Capturing parallel behavior
̶ Consist of a two and more regions
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State Machine Diagram in OOP world
̶ In our case, state machine diagram is used to represent lifecycle
of an object
̶ Context of the diagram is only the instance of a class from
design class diagram
̶ All methods and events must be supported by the design class diagram
̶ Initial transition means calling the constructor
̶ Final transition means deleting the object from system
̶ Object saves its state even outside main memory (persistence)
PB007 Software Engineering I — Getting Dynamic, State Machine Diagram10
State Machine Diagram in OOP world
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You gotta do what you gotta do
Task for this week
̶ Process the feedback
̶ Choose a suitable object for modeling
̶ Something with non-trivial lifecycle
̶ Create a state machine diagram for this object
̶ Revise design class diagram if needed
̶ Do your part in peer review