Confused in Use Case Diagram

> [Actor]-->(USE CASE)-->[Actor]

Is just more explicit than

> [Actor](USE CASE)[Actor]

When adding arrows you you add more meaning to the diagram. Without arrows you don't know how the interaction between the actor and the use case really is.

Example,

> [Actor]-->(USE CASE)-->[Actor]

Could be that one actor invokes something in a system that will alert another actor.

allan.lykkea at 2007-7-12 14:24:38 >

To echo what the other two respondents already covered, it simply provides more information about the interaction between the actor and the use case. That being said, as soon as I see this type of directed interaction it immediately leads me to ask "what makes this interaction only one way?" and "is there ever a time where the interaction will be reversed?".

Jonathan House

jonathanhousea at 2007-7-12 14:24:39 >

Well, when you << include >> a use-cause it means that it comes before (just like when you are programming and choose to include code).

In the second example:

[update news]--include-->[save news]

you would use an << extend >> instead.

You can use << extend >> when one use-case is an option in another use-case.

Example, The user wants a system where he can click to update a news item. If he makes any changes he wants to be able to click on a widget to save the changes.

This could be expressed as:

[update news]-- << extend >> -->[save news]

allan.lykkea at 2007-7-12 14:24:39 >

i agree that <<include>> does not imply any ordering.

however, <<extends>> can be used with an "extension point" that defines a point from which the use case can be extended. A condition is associated with the extension point so that a use case instance can choose whether or not to perform the functionality defined in the extending use case.

there is a detailed explanation with examples in the UML specifications in Section 2(Semantics) . Use Cases - detailed semantics. available from www.omg.org/uml.

regards,

Alex

al_bagehota at 2007-7-12 14:24:39 >