27-08-2012, 12:17 PM
Using Use Case Diagrams
1Using Use.ppt (Size: 86.5 KB / Downloads: 279)
Use case diagrams are used to visualize, specify, construct, and document the (intended) behavior of the system, during requirements capture and analysis.
Provide a way for developers, domain experts and end-users to Communicate.
Serve as basis for testing.
Use case diagrams contain use cases, actors, and their relationships.
Use Case
Use cases specify desired behavior.
A use case is a description of a set of sequences of actions, including variants, a system performs to yield an observable result of value to an actor.
Each sequence represent an interaction of actors with the system.
Specifying the Behavior of a Use Case
Describing the flow of events within the use case.
Can be done in natural language, formal language or pseudo-code.
Includes: how and when the use case starts and ends; when the use case interacts with actors and what objects are exchanged; the basic flow and alternative flows of the behavior.
Actors
An actor represents a set of roles that users of use case play when interacting with these use cases.
Actors can be human or automated systems.
Actors are entities which require help from the system to perform their task or are needed to execute the system’s functions.
Actors are not part of the system.
Use Cases and Actors
From the perspective of a given actor, a use case does something that is of value to the actor, such as calculate a result or change the state of an object.
The Actors define the environments in which the system lives
Relationships between Use Cases
1. Generalization - use cases that are specialized versions of other use cases.
2. Include - use cases that are included as parts of other use cases. Enable to factor common behavior.
3. Extend - use cases that extend the behavior of other core use cases. Enable to factor variants.