SysML Sequence Diagram

SysML Sequence Diagram⌘

Sequence Diagram⌘

• Participants are represented by lifeline - a rectangle and a dashed line
• Messages are represented by arrows between lifelines
• Lifeline describes the time-line for a process, where time increases down the page
• The entire diagram represents one interaction

Lifeline⌘

Lifeline

• a set of instances
• can be considered as objects of the specified type
• represents a participant

Occurrence Specification ⌘

• Occurrence Specification represents a moment in time at the beginning or end of a message or at the beginning or end of an execution.
• The semantics of an Interaction is given as a trace (a sequence of event occurrences).

Execution Specification ⌘

• Specification of the execution of a unit of behavior within the lifeline.
• Sending and receiving messages determine start and end of execution specification.

Message⌘

Message Types⌘

• Synchronous message (filled arrowhead):
  • caller waits until called behavior terminates
  • reply message is represented by dashed line with either an open or filled arrow head
• Asynchronous message (open arrowhead):
  • caller doesn't wait but continues after call, no reply
• Found message (open arrowhead originating from a filled circle):
  • receiver known, sender not known
• Lost message (open arrowhead pointing to a filled circle)
  • sender known, receiver not known
• Create message (dashed line with open arrowhead pointing to header of lifeline):
  • new lifeline is created at this point in the diagram
• Delete message (open arrowhead):
  • object destruction, stop (destruction of an object is represented by a cross on the lifeline)

Event Occurrences⌘

• Sequence of event occurrences (trace) is defined by <eventoccurrence1, eventoccurrence2, ...,eventoccurrence-n>
• send event is denoted by an exclamation mark (!p)
• receive event is denoted by question mark (?p)
• A valid sequence for the interaction: < !p, ?p, !q, ?q >
• It's not the only valid sequence!

Event Occurrences valid trace⌘

Event Occurrences Rule⌘

• Send event before receive event
• The order of events along one lifeline is relevant.
• The position of one event relative to an event on another lifeline is insignificant.

Fragments⌘

• Combined Fragment is an interaction fragment which defines a combination (expression) of interaction fragments.
  • Interaction Operator specifies the meaning of Combined Fragment
  • Interaction Operands are separated by a dashed horizontal line. The Interaction Operands together make up the framed Combined Fragment
  • Interaction Constraint is shown in square brackets covering the lifeline where the first event occurrence will occur, positioned above that event

Interaction Operator Kind⌘

Only one operand fragments		One or more operands fragments
opt - option	neg - negative	alt - alternatives
break	assert - assertion	par - parallel
loop- iteration	consider	strict - strict sequencing
critical	ignore	seq - weak sequencing

Interaction Use⌘

• Interaction Use is an interaction fragment which allows to use another interaction.
• It is shown as a Combined Fragment symbol where the operator is called ref.

Interaction Use referring the Interaction EstablishAccess with (input) argument “Illegal PIN.” Within the optional CombinedFragment there is another Interaction Use without arguments referring OpenDoor

Interaction Use example⌘

Sequence diagram example⌘