Sequence diagram

Sequence diagram

A sequence diagram is a kind of interaction diagram in UML, that shows how processes operate one with another and in what order. It is a construct of a Message Sequence Chart.

Overview

A sequence diagram shows, as parallel vertical lines ("lifelines"), different processes or objects that live simultaneously, and, as horizontal arrows, the messages exchanged between them, in the order in which they occur. This allows the specification of simple runtime scenarios in a graphical manner.

-->If the lifeline is that of an object, it is underlined (if not it is a role). Note that leaving the instance name blank can represent anonymous and unnamed instances.

In order to display interaction, messages are used. These are horizontal arrows with the message name written above them. Solid arrows with full heads are synchronous calls, solid arrows with stick heads are asynchronous calls and dashed arrows with stick heads are return messages. This definition is true as of UML 2, considerably different from UML 1.x.

Activation boxes, or method-call boxes, are opaque rectangles drawn on top of lifelines to represent that processes are being performed in response to the message (ExecutionSpecifications in UML).

Objects calling methods on themselves use messages and add new activation boxes on top of any others to indicate a further level of processing.

When an object is destroyed (removed from memory), an X is drawn on top of the lifeline, and the dashed line ceases to be drawn below it (this is not the case in the first example though). It should be the result of a message, either from the object itself, or another.

A message sent from outside the diagram can be represented by a message originating from a filled-in circle ("found message" in UML) or from a border of sequence diagram ("gate" in UML).

A UML diagram may perform a series of steps, called a superstep, in response to only one external stimulus.

Usage and limitations

Some systems have simple dynamic behavior that can be expressed in terms of specific sequences of messages between a small, fixed number of objects or processes. In such cases sequence diagrams can completely specify the system's behavior. Often, behavior is more complex, e.g. when the set of communicating objects is large or highly variable, when there are many branch points (e.g. exceptions), when there are complex iterations, or synchronization issues such as resource contention. In such cases, sequence diagrams cannot completely describe the system's behavior, but they can specify typical use cases for the system, small details in its behavior, and simplified overviews of its behavior.

References

External links

* [http://www.uml.org Current UML Specification] by Object Management Group (OMG)
* [http://www.agilemodeling.com/artifacts/sequenceDiagram.htm Introduction to UML 2 Sequence Diagrams] by Scott W. Ambler.
* [http://www.agilemodeling.com/style/sequenceDiagram.htm UML 2 Sequence Diagram Guidelines] by Scott W. Ambler.
* [http://www-128.ibm.com/developerworks/rational/library/3101.html UML's Sequence Diagram] by Donald Bell
* [http://sdedit.sourceforge.net/ A simple SD editor]
* [http://www.websequencediagrams.com/ Web-based Sequence Diagram Generator]
* [http://www.tracemodeler.com/articles/a_quick_introduction_to_uml_sequence_diagrams/index.html A Quick Introduction to UML Sequence Diagrams] by Yanic Inghelbrecht
* [http://www.tracemodeler.com Trace Modeler : Smart editor for UML sequence diagrams, combines automatic layout with a simple drag & drop interface]
* [http://www.tracemodeler.com/gallery/index.html A gallery with many examples of UML sequence diagrams]
* [http://www.codeswat.com/cswat/index.php?option=com_content&task=view&id=70&Itemid=101 Flowchart4j - Generates Sequence diagram from Java code, also exports to Microsoft Visio as UML Model Diagram.]
* [http://www.eventhelix.com/eventstudio/ EventStudio: Generate Sequence Diagrams from Text Based Model]
* [http://www.MaintainJ.com MaintainJ - Eclipse plugin to generate runtime sequence diagrams for a use case for any Java application.]
* [http://home.planet.nl/%7Eborst595/ Dynamic Sequence Diagram Viewer: Generate and update (via XML) real time animated dynamic sequence diagrams within a web page] by Richard Jewson.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • System Sequence Diagram — In software engineering, a System Sequence Diagram (SSD) is a sequence diagram that shows, for a particular scenario of a use case, the events that external actors generate, their order, and possible inter system events. System sequence diagrams… …   Wikipedia

  • Diagram — Further information: Chart Sample flowchart representing the decision process to add a new article to Wikipedia. A diagram is a two dimensional geometric symbolic representation of information according to some visualization technique. Sometimes …   Wikipedia

  • Séquence principale — Le diagramme de Hertzsprung Russell figure les étoiles. En abscisse, l indice de couleur (B V) ; en ordonnée, la magnitude absolue. La séquence principale se voit comme une bande diagonale marquée allant du haut à gauche au bas à droite. Ce… …   Wikipédia en Français

  • Communication diagram — Example of a Communication diagram. UML diagrams Structural UML diagrams Class diagram …   Wikipedia

  • Interaction overview diagram — in the Unified Modeling Language (UML) is a type of activity diagram in which the nodes represent interaction diagrams. They are a s high level structuring mechanism for sequence diagrams. Interaction overview diagrams illustrate an overview of a …   Wikipedia

  • Hubble sequence — The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1936.cite book |last=Hubble |first=E. P. |authorlink=Edwin Hubble |title=The Realm of the Nebulae |year=1936 |publisher=Yale University Press… …   Wikipedia

  • Object diagram — Example of a Object diagram. UML diagrams Structural UML diagrams …   Wikipedia

  • Composite structure diagram — UML diagrams Structural UML diagrams Class diagram Component diagram Composite structure diagram Deployment diagram Object diagram …   Wikipedia

  • Class diagram — UML diagrams Structural UML diagrams Class diagram Component diagram Composite structure diagram Deployment diagram Object diagram …   Wikipedia

  • Deployment diagram — A sample deployment diagram UML diagrams Structural UML diagrams …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”