284:(UML) is needed to construct a system sequence diagram. These models show the logic behind the actors (people who affect the system) and the system in performing the task. Reading a sequence diagram begins at the top with the actor(s) or the system(s) (which is located at the top of the page). Under each actor or system there are long dotted lines, called "lifelines", which are attached to them. Actions are performed with lines that extend between these lifelines. The connection between an action line and a lifeline shows the interaction between the actor or system. Messages will often appear at the top or bottom of a system sequence diagram to illustrate the action in detail. For example, a request by an actor to log in would be represented by login (username, password). After each action is performed, the response or next action is located under the previous one. By reading down the lines, one can see in detail how certain actions are performed in the provided model, and in what order.
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shows process interactions arranged in time sequence. This diagram depicts the processes and objects involved and the sequence of messages exchanged as needed to carry out the functionality. Sequence diagrams are typically associated with use case realizations in the
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Professionals, in developing a project, often use system sequence diagrams to illustrate how certain tasks are done between users and the system. These tasks may include repetitive, simple, or complex tasks. The purpose is to illustrate the
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If the lifeline is that of an object, it demonstrates a role. Leaving the instance name blank can represent anonymous and unnamed instances. → Messages, written with horizontal
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UML has introduced significant improvements to the capabilities of sequence diagrams. Most of these improvements are based on the idea of
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with the message name written above them, display interaction. Solid arrow heads represent synchronous calls, open arrow heads represent
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223:: A regular version of sequence diagram describes how the system operates, and every object within a system is described specifically.
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Objects calling methods on themselves use messages and add new activation boxes on top of any others to indicate a further level of
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which represent smaller pieces of an enclosing interaction. Multiple interaction fragments are combined to create a variety of
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A message sent from outside the diagram can be represented by a message originating from a filled-in circle (
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of the system under development. Sequence diagrams are sometimes called
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456:"About the Unified Modeling Language Specification Version 2.5.1"
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A system sequence diagram should specify and show the following:
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OMG Unified
Modeling Language (OMG UML), Superstructure, V2.1.2
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OMG Unified
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OMG Unified
Modeling Language (OMG UML), Superstructure, V2.4.1
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Standards
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Return values (if any) associated with previous messages
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A sequence diagram shows, as parallel vertical lines (
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475:A Quick Introduction to UML Sequence Diagrams
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954:List of Unified Modeling Language tools
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380:Unified Modeling Language 2.5.1
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304:. Activation boxes, or
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488:UML 2 Sequence Diagrams
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389:Object Management Group
288:Diagram building blocks
86:Behavioral UML diagrams
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18:System sequence diagram
359:Message sequence chart
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377:"Sequence Diagrams".
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442:. p. 467.
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338:in UML).
321:destroyed
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883:Sequence
862:Use case
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686:Activity
679:Behavior
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478:Archived
353:See also
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207:use case
177:Overview
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229:: All
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