Timing and Interaction Overview Diagrams

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Timing and Interaction Overview Diagrams

• Keng Siau
• University of Nebraska-Lincoln

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Timing Diagrams

• A timing diagram is an interaction diagram that
  shows actual times across different objects or
  roles
• Instead of relative sequences of messages
• An alternative way of displaying a sequence
  diagram that explicitly shows changes in state on
  a lifeline and metric time (time units)
• Useful in real-time applications

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Timing Diagrams
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Timing versus Sequence Diagrams

• The axes are usually reversed so that time
  increases from left to right
• Lifelines are shown in separate compartments
  arranged vertically
• The lifeline jogs up and down to show changes in
  state
• Each vertical position represents a different
  state
• The ordering of states may or may not have any
  significance

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Timing versus Sequence Diagrams

• Alternatively, a lifeline can follow a single
  line with different states or values displayed on
  the line
• A metric time axis may be shown
• Tick marks indicate time intervals, sometimes
  discrete times at which changes happen
• The time on different lifelines are synchronized
• The value held by an object may be shown

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Interaction Overview Diagrams

• An interaction overview diagram is a hybrid of an
  activity diagram and a sequence diagram
• An activity diagram incorporating sequence
  diagram fragments together with flow of control
  constructs
• It shows sequence diagram notations with decision
  and fork notations from activity diagrams
• The control symbols show the high level flow of
  control among the nested symbols, which can
  contain sequences including messages

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Example of an Interaction Overview Diagram