PB007 Software Engineering I — Interaction Diagrams, Sequence Diagram1
Interaction Diagrams,
Sequence Diagram
PB007 Software Engineering I
Lukáš Daubner
daubner@mail.muni.cz
PB007 Software Engineering I — Interaction Diagrams, Sequence Diagram2
Interaction Diagrams
̶ Model collaboration between classes/objects/actors
̶ i.e., communication between them
̶ Describes:
̶ Method execution
̶ Scenarios
̶ Collaboration of subsystems
̶ …
̶ In general, they model behavior and communication between two
and more objects
̶ In contrast to State Diagram, which focuses only on inner behavior of one object
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Communication Diagram
̶ Captures the communication with focus on relationships between
objects
̶ Interaction is considered as their entanglement
̶ From the object point of view, they describes detailed execution of
a use case (or its part)
̶ Again, everything must be consistent with Class Diagram
̶ Link can exist only if there is a reference (association or dependency)
̶ Messages are method calls on receiving object
̶ We work with object – instances of classes
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Communication Diagram – Example
Link
Message
Object
Object Creation Message
Return Message
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Sequence Diagram
̶ Captures the communication with focus on time-based ordering of
messages
̶ Interaction is considered as a sequence of messages
̶ From the object point of view, they describes detailed execution of
a use case (or its part)
̶ Again, everything must be consistent with Class Diagram
̶ Link can exist only if there is a reference (association or dependency)
̶ Messages are method calls on receiving object
̶ We work with object – instances of classes
̶ Mind the ordering, objects cannot receive message before their creation
̶ Calls in one context must be in the same activation (focus of control)
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Sequence Diagram – Example
Return message
Message
Lifeline
Activation
Creation message
Time
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Sequence Diagram – Example
Nested activation
Destruction message
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Combined Fragments
̶ Divides the sequence diagram into areas with different behavior
̶ They include operator, at least one operand and zero or more
conditions
̶ Examples of major operators:
̶ opt (option) – one operand, which is executed only if the specified condition is satisfied
̶ alt (alternatives) – multiple operands, only the one with the satisfied condition is executed
̶ loop – repeated execution of the operand
̶ break – executed if its condition is satisfied, and it terminates the execution cycle
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Combined Fragments – Example
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Combined Fragments – Example
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You gotta do what you gotta do
Task for this week
̶ Process the feedback
̶ Based on the Use Case Diagram and Design Class Diagram, think
about the interaction between the objects that are participating in
the use case
̶ You can write it down as a pseudocode – it could help you
̶ Choose three cases and model them into three Sequence
Diagram
̶ If you need to change something in Design Class Diagram, just do it, no worries.
̶ Do your part in peer review