It describes & related to the
external observation of system .It describes the main interactions between the system
and external entities, including users and other systems. It describes the main
user roles with the help of diagram.
Components of a Use case Diagram
Actor: Represents the role played with external entities to the System.
Use Case: Describe the interaction between actor’s and the system. It will describe what system will do (Functionality).
Relationships:
– Association between actors and use cases.
– Extension (or generalization) among actors.
– Dependency among use cases: include and extend.
The difference between include & extend is :-
<<Include>> means reuse of functionality (i.e. the included functionality is used or could be used elsewhere in the system). Include therefore denotes a dependency on another use case.
<<Extends>> means adding (not reusing) functionality and also any optional functionality. Extends therefore can denote one of two things: 1. adding new features/capabilities to a use case (optional or not) 2. any optional use cases (existing or not).
Example
Components of a Use case Diagram
Actor: Represents the role played with external entities to the System.
Use Case: Describe the interaction between actor’s and the system. It will describe what system will do (Functionality).
Relationships:
– Association between actors and use cases.
– Extension (or generalization) among actors.
– Dependency among use cases: include and extend.
The difference between include & extend is :-
<<Include>> means reuse of functionality (i.e. the included functionality is used or could be used elsewhere in the system). Include therefore denotes a dependency on another use case.
<<Extends>> means adding (not reusing) functionality and also any optional functionality. Extends therefore can denote one of two things: 1. adding new features/capabilities to a use case (optional or not) 2. any optional use cases (existing or not).
Example
Use Case Table
|
Use
Case ID
|
Check Grades
|
|
Actors:
|
Student
|
|
Description:
|
View the grades of a specific year and semester |
|
Preconditions:
(=
Entry Condition)
|
The
student is already registered
|
|
Triggers
|
- Main
menu event
|
|
Post-conditions:
(=
Exit Condition)
|
|
|
Normal
Course:
|
1.
The system carries out “Validate User”, e.g.,
for
user “miner” with password “allAs”.
2 The
system prompts for the year and semester.
3. The system displays the grades of the
courses. taken
in the given semester, i.e., Fall 2013.
|
|
Alternative
Courses:
(Optional)
|
The
student enters “All” for the year and semester, and the system displays |
|
Exceptions:
(=also
Boundary conditions)
|
The “Validate User” use case fails; the system repeats the validation use case. |
|
Technical
Perspective:
|
-
|
|
Includes:
|
NIL
|
|
Frequency
of Use:
|
Frequently
|
|
Assumptions:
|
NIL
|
|
Notes:
|
NIL
|
|
Issues:
|
NIL
|
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