Page 112 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Object Oriented Analysis and Design

Notes
• The system waits for the ring count to reach the answering ring count.
• The system plays a greeting.
• The system performs mode specific processing.
Postconditions: The answering machine prepares for the next caller.
Alternative • The caller hangs up phone during the playing of the greeting.
Course • The system recognizes hang-up, stops greeting and prepares for the next
caller.
Extensions Take Caller Message
Decision Support Frequency: This use is triggered on every incoming call when machine is set
to answering mode.
Modification Owner: Project Group A, XYZ Ltd.
History Initiation Date: January 17, 2005.
Date Last Modified: January 27, 2005.
Question

Illustrate the Use Case Diagram for the Answering System.
Source: http://gyan.frcrce.ac.in/~surve/OOAD/UCD/UCD_CaseStudy.html

8.4 Summary

A relationship between two use cases is basically a dependency between the two use cases.
Defining the relationship between two use cases is the decision of the modeler of the use
case diagram.

The participation of an actor in a use case is shown by connecting the actor symbol to use
case symbol by a solid path. The actor is said to ‘communicate’ with the use case.
An extends shows the relationships between use cases. Relationship between use case A
and use case B indicates that an instance of use case B may include the behavior specified
by A.

When a use case is depicted as using functionality of another functionality of another use
case, this relationship between the use cases is named as an include or uses relationship.
A generalization relationship is a parent-child relationship between use cases. In a use
case diagram, generalization is shown as a directed arrow with a triangle arrowhead.
An object remains active after sending a message and can reply to other messages without
waiting for a response.

Guard conditions can be used to show that one of a set of concurrent threads is conditional.
An activity state may reference another activity diagram, which shows the internal structure
of the activity state.

8.5 Keywords

Active object: An active object owns a thread of control.
Communicates relationship: A communicates relationship between an actor and a use case
indicates that the actor initiates the use case.

Extends: An extends shows the relationships between use cases.
Generalisation: A generalisation relationship between actors or use cases indicates that one
actor or use case (the child) inherits the characteristics of another actor or use case (the parent).

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