invoke/extend/include in structured scenario

[vjr]

• What's the practical benefit of linking to use cases in this way?
• What's the difference between extend and invoke, specifically?

Thanks

[Geert Bellekens]

What do you mean by "invoke"?
I only know include and extend.
Suppose
UCA --include--> UCB
UCA <--extend-- UCB

Notice the difference in direction of the relation. In both cases UCB contains behavior that may be executed during the execution of UCA.
The difference is that in case of an include UCA knows about UCB and decides when to execute it.
In case of Extent UCA only provide extension points (consider them hooks) which UCB can use to execute its own behavior, without the knowledge of UCA.

Geert

[vjr]

What do you mean by "invoke"?
I only know include and extend.
Suppose
UCA --include--> UCB
UCA <--extend-- UCB
Notice the difference in direction of the relation. In both cases UCB contains behavior that may be executed during the execution of UCA.
The difference is that in case of an include UCA knows about UCB and decides when to execute it.
In case of Extent UCA only provide extension points (consider them hooks) which UCB can use to execute its own behavior, without the knowledge of UCA.

Geert

[edit]Sorry for the confusion, I wasn't asking what include/extend means. I'm still trying to understand the Structured Scenario editor and how I can make use of it. (viz my my previous post on it).

Try this: right-click a scenario step. A pop-up menu appears. Choose Link Step to UseCase. In the sub-menu, three more options appear: <<extend> UseCase/<<include>> UseCase/[Invokes: UseCase].

EA adds the appropriate relationship between the chosen use cases, extend/include/invokes respectively, as the help text states.

"Either include the actions of an existing Use Case element, extend an existing Use Case element, or invoke a Use Case as the action of the selected step. Selecting the appropriate sub-option displays the Select Use Case dialog, which you use to browse for and select the required Use Case element.

The appropriate includes, extends or invokes stereotyped connector is created between the current element and the selected Use Case.

For the include and extend actions, any text in the Action field is overwritten by the link to the Use Case. For the invoke action, the following link is added to the end of the Action text:

[Invokes: <Use Case Name>]"

However, this doesn't really tell me what the use-case   for this feature is.
[/edit]