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Sequence diagram example
What is the purpose of sequence diagram ?
The sequence diagram is used primarily to show the
interactions between objects
in the sequential order that those interactions occur.
Developers think sequence diagrams were meant exclusively for them
Business staff can find sequence diagrams useful to communicate how the business currently works by showing how various
business objects interact
A business-level sequence diagram can be used as a
During the requirements phase use cases are often refined into
one or more sequence diagrams
Sequence vs. Activity?
Little bit later…Slide4
An empty frameLifelineSlide5
Sending a message/methos to another objectThe name is placed above the arrowed lineAnd represents an operation/method that the receiving object's class implements.Slide6
Return messages – optionalThe use of return messages depends on the level of detail/abstractionReturn value is placed above dotted lineSlide7
Sending a message to itselfthe model draws attention to the fact that this processing takes place in the system object.Slide8
Who will guard the guardians themselves?Who will guard the guardians themselvesSlide10
Combined fragments (alternatives, options, and loops)
A combined fragment is used to group sets of messages together to show
in a sequence diagram.
Alternatives - classic "if then else" logic
Options - a simple "if then" without “else”
Loops – a repetitive sequenceSlide11
mutually exclusive choice between messagesSlide12
used to model a sequence that, given a certain condition, will occur; otherwise, the sequence does not occur.Slide13
does not require guard condition be placed on ita guard can have two special conditionsMinint = 1, Maxint = 5Slide14
most commonly used to model exception handlingcause the exiting of an enclosing interaction's sequence. In cases where a break is part of combined fragment, then only that fragment is exited.Slide15
Referencing another sequence diagramSlide16
Sequence(SD) vs. activity (AD)?
AD mainly represent process flows.
SD mainly represent
step by step
ordered in time interaction between different objects.
AD also repersents an object role in workflow but level of repersenation is not dynamic like SD.
Example: Object lifeline and detailed sequence of interactionSlide17
Online bookshop exampleSlide18
Facebook user authentication in a Web applicationSlide19
Submit comments (AJAX)Slide20Slide21Slide22Slide23