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subject > representation > coding technique > diagram > UML diagram > interaction diagram > sequence diagram > simple sequence diagram

simple sequence diagram
subject			fact

simple sequence diagram	can be converted into a collaboration diagram
	is a subtopic of 8.1 - Interaction Diagrams
	is a kind of sequence diagram
sequence diagram	arranges objects from left to right across the diagram with an actor that initiates the interaction often shown on the left
	has part activation box
	has part iteration expression
	has part lifeline
	is better than collaboration diagram when: You want the reader to be able to easily see the order in which messages occur You want to build an interaction model from a use case You need to show details of messages, such as parameters and return values
	represents iteration over objects by preceding the message name with an asterisk, and showing an iteration expression in square brackets
	represents message as an arrow between activation boxes of the sender and receiver
	represents time as the vertical dimension with time progressing downwards to the bottom of the diagram
	shows the destruction of an object using a big 'X' symbol on a lifeline
	shows the sequence of messages exchanged by the set of objects (and optionally an actor) performing a certain task
interaction diagram	can be used to define the protocol used when two components communicate with each other
	can contain more or less detail depending on what you wish to communicate
	has purpose to better understand the sequence of messages
	helps you to visualize how the system runs
	models the dynamic aspects of a software system
	should be created after developing a class diagram and a use case model because you need to know the actors and objects involved in an interaction
UML diagram	describes aspects of the architectural model
	has part constraint
	has part note
	see also Unified Modelling Language
diagram	has advantages it conveys or summarizes complex concepts or mechanisms more easily than other techniques
	has problems can be hard for users to interact with or interpret not usable by blind people it can be expensive to program diagram drawing software
	should have a label if its meaning is not obvious, using a caption or pop-up label that appears when the user moves the mouse over it

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