How to Create Sequence Diagrams.

How to Create a Software Design Document for Vu Projects Cs619 Help.
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How to Create Sequence Diagrams.

Post by ALI RAZA » Tue May 08, 2018 7:45 am

A sequence diagram shows object interactions arranged in time sequence. It depicts the objects and classes involved in the scenario and the sequence of messages exchanged between the objects needed to carry out the functionality of the scenario.

Sequence diagrams describe interactions among classes in terms of an exchange of messages over time. They're also called event diagrams. A sequence diagram is a good way to visualize and validate various runtime scenarios. These can help to predict how a system will behave and to discover responsibilities a class may need to have in the process of modeling a new system.
Basic Sequence Diagram Notations
Class Roles or Participants

Class roles describe the way an object will behave in context. Use the UML object symbol to illustrate class roles, but don't list object attributes.


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Activation or Execution Occurrence
Activation boxes represent the time an object needs to complete a task. When an object is busy executing a process or waiting for a reply message, use a thin gray rectangle placed vertically on its lifeline.

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Messages
Messages are arrows that represent communication between objects. Use half-arrowed lines to represent asynchronous messages. Asynchronous messages are sent from an object that will not wait for a response from the receiver before continuing its tasks. For message types, see below.
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Lifelines
Lifelines are vertical dashed lines that indicate the object's presence over time.

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Destroying Objects
Objects can be terminated early using an arrow labeled "<< destroy >>" that points to an X. This object is removed from memory. When that object's lifeline ends, you can place an X at the end of its lifeline to denote a destruction occurrence.

Loops
A repetition or loop within a sequence diagram is depicted as a rectangle. Place the condition for exiting the loop at the bottom left corner in square brackets [ ].

Types of Messages in Sequence Diagrams
Synchronous Message
A synchronous message requires a response before the interaction can continue. It's usually drawn using a line with a solid arrowhead pointing from one object to another.

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Asynchronous Message
Asynchronous messages don't need a reply for interaction to continue. Like synchronous messages, they are drawn with an arrow connecting two lifelines; however, the arrowhead is usually open and there's no return message depicted.

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Reply or Return Message
A reply message is drawn with a dotted line and an open arrowhead pointing back to the original lifeline.
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Self Message
A message an object sends to itself, usually shown as a U shaped arrow pointing back to itself.

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Create Message
This is a message that creates a new object. Similar to a return message, it's depicted with a dashed line and an open arrowhead that points to the rectangle representing the object created.

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Delete Message
This is a message that destroys an object. It can be shown by an arrow with an x at the end.

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Found Message
A message sent from an unknown recipient, shown by an arrow from an endpoint to a lifeline.

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Lost Message
A message sent to an unknown recipient. It's shown by an arrow going from a lifeline to an endpoint, a filled circle or an x.

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Sample Diagram

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