UML - Use Cases

[Sarikaa Bhatnagar]

Hello All,

I am new to UMl and in the process of learning. Can someone tell me whether we identify the actors for each module or for the entire system.

Secondly, is the task performed by each actor is one use case.

Thanks,

[Padmaja Godbole]

Hi Sarika,

Following is my understanding about the Use Cases :

Use Cases define the scope of the system, they are very similar to requirements, they enable us to visualise size and scope of the entire development.

The sum of the use cases is the whole system, that means anything not covered by a use case is out side the boundary of the system we are developing

Now the answer of your question is :
One can identify Actors for a Module as well as for the whole system, it depends upon the UML diagram he/she is preparing for.

Use Cases that are presenting a Module will include actors involved in that Module only.
[ May 11, 2005: Message edited by: Padmaja Godbole ]

[Padmaja Godbole]

And also task performed by each actor will be a use case but granular tasks should not be included, only the main main tasks will make the possible Use Cases.

Is my understanding up to the mark ranchers?

[Scott Ambler]

You might find some of the links at Agile Models Distilled to be helpful. There are several links to use case related topics.

- Scott

[Sarikaa Bhatnagar]

Hey Scott,

Thanks a lot! The link is really good and useful

[Ilja Preuss]

Also notice that the bubbles in use case *diagrams* are just placeholders for the *actual* use cases, which are textual.

Depending on the reason for modeling use cases, getting the different types of actors right probably isn't particularly important.

[Stan James]

Showing different types of actors is sometimes helpful when communicating with business folks, but they don't always affect the software much. If you know you have to have a mechanism for things some users can do and others cannot, it will probably handle 2 types of actors or 200 the same. Non-human actors are interesting to me because they imply some kind of protocol and API with other systems.

[Scott Ambler]

The line between an actor and a use case implies an interface of some sort. When the actor is a human, it's a user interface. When the actor is a system, it's a system interface.

- Scott