UML Use case diagram
UML Use case diagram in Information Systems Development
To help you understand what is UML (Unified Modeling Language) – UML use case diagram. I will answer here the most explain and example clear about use case in Information Systems Development.
The UML use case diagram has three main components:
Actors: The roles adopted by those participating
Use cases: High-level activities to be supported by the system
Links: Which actors are involved in which use cases
A use case is drawn as an ellipse with the name inside the ellipse or below it
figure 1 UML use case diagram
Use cases include a graphical representation of actors, use cases, and four kinds of relationships (Fowler, 1999; Rumbaugh et al., 1999):
The association relationship establishes the communication between an actor and a use case. The include and extend relationships are stereotyped by the words: «include» and «extend». The generalization relationship allows a specialized use case to change any aspect of the base use case.
The following are a number of key points concerning the actor in a use case model.
An actor indicates an external person or system
An actor may be a set of rules, which are related
An actor may be involved in more than one use case
One actor is normally the initiator of each use case
figure 2 actor UML use case diagrams
The link from an actor to a use case can be shown with navigability.
An example UML use case diagrams is shown below:
Association Navigability UML use case diagrams
There can be relationships between use cases to show dependencies. The two relationships supported are extended and includes. The notation is illustrated below:
figure 4 Extend UML use case diagrams
If one use case extends another, it adds behavior under certain conditions.
Note that the actor is only linked with the primary use case. An example is shown below:
figure 5 UML use case diagrams
One use case can include all the behavior of another use case.
The additional behavior is included at a place indicated in the detailed description of the use case that includes it.
Here I wrote the structure of a use case document can vary, but a typical description would contain
Preconditions necessary for the use case to start
A detailed description of the flow of events that include:
Main flow of events that can be broken down to show
Sub flows of events
Alternative flows to define exceptional situations
Post-conditions that define the state of the system after the use case ends
The use case document evolves with the development progress. In the early stage of requirements determination, only a brief description is written – as shown below with the bank scenario – DEPOSIT.
A customer passes to the bank an amount of money, in some combination of cash and cheques. The customer states which account is to be updated. The teller checks the money and authorizes the updating of the relevant account. If the money is incorrect or the account does not exist the teller informs the customer, returns the money and the account is not updated.
figure 8 :
The customer is the actor that initiates the deposit.
The inputs to the use case are identified.
The outcomes are identified.
- The end
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