Use cases scenarios and activity diagrams

[mchiuminatto]

Hi.

Does anybody knows a formal or known technique to express use case scenarios as activity diagrams?, mainly to represent  inclusion, extension and generalization points.

TIA

[Oscar]

Marcello,

I'm not sure if it is exactly what your trying to accomplish, but have a look at "Use Case Maps"
(http://www.usecasemaps.org )


Oscar

[jps]

I don’t know of any formal technique, but what immediately jumps to mind is to simply model inclusions and extensions as a Subactivities.  I’m not sure exactly how you are using generalization, so I’m not sure if that would work for generalization or not.

Of course, another option is to not use activity diagrams at all but instead use what Larman calls System Sequence Diagrams.  

Best regards,

James

[mchiuminatto]

Thanks Oscar and James.

We are trying Activity Diagrams as a way to check consistency of plain text scenario description. Some books mention it as an alternate way to describe scenarios, but I agree with Fowler when he says that for domain experts can be a little bit hard to follow so that’s the reason we are just using it as a consistency check mechanism.

I’ll give a further read to System Sequence Diagrams.

Thanks

[Stephen]

Another option for the more diligent modeller is to use Collaboration Diagrams, rather than Activity Diagrams.

You do need to educate your less-technical readers to get the most out of them, but they can help you make sure you don't miss any objects out on your journey from use-cases to detailed architecture.

Just as you can map a process onto a sequence diagram it goes onto a collaboration, but makes a more compact diagram!

[Stephen]

Of course (!) you need to decide exactly what it is you're after. Formally Collaboration diagrams model interactions between objects as messages.

If your modelling process or data flow the "correct" model is the activity diagram.

I'm prepared to bet that most readers won't spot the difference - although its always a very good idea to not get messages and data flow mixed up.

[sargasso]

Just to take this to one of my typically illogical extremes...

Is there a way of converting an activity diagram back into a scenario or set of scenarios?  :-/

The reason I ask is related to the other thread on getting scenarios into test cases.  We have just completed a model that took a bit of effort to get the activity model sorted - its quite complex with (at least)zillions of alternate flows.

It would be "real good" if there was some way to get these flows back into the test cases automatically.

Bruce

[fluxtah]

Not sure if this relates but in ICONIX they use a diagrams called Robustness Diagrams which is based on noun verb analysis of use case text to check the consistency of use case descriptions.

ICONIX say these diagrams where excluded from UML spec because they are a prime cause of analysis paralysis, however they are supposed to be a 10 minute throw away diagram, only created to ensure there are no ambiguities in use case descriptions.

regards

Ian

[mchiuminatto]

Hi everybody, sorry the delay on reply, but I was a little bit busy.

About  your question sargasso,  if  there's any way to get one or more scenario from an activity diagram, I  "almost" found a way. The procedure is:

1. After you describe your use cases scenarios in terms of activities you assign three taged values to each activity:

a) Use Case: The use case it belongs to,
b) The Scenario: A Scenario Identifier, for instance BP (BAsic Path), A1 (Alternate 1), E1 (Exception 1) and so on.
c) A Squence number, for instance SQ1, (step1), SQn (Step n)


3. Export your model to a Database Repository

4. Using the power of SQL you can retrieve a list of activity description, ordered by sequence number, per scenario, per uscase; joining the object table and the taggedvalues table.

But here comes the reason why I "almost" found it. . EA does not export tagged values to the t_taggedvalues table of the EA repository Model.

I dont' know if this is a bug,  may be I'm confussed on the use of the t_taggedvalue table  or is a bug located between the keyboard and the chair.

[mchiuminatto]

Finally, it was a bug located between de keyboard and the chair. The table where the tagged values are stored is: t_objectproperties.

[mchiuminatto]

FYI.


"I've recently begun to create a single activity diagram for each use case in the system. This activity diagram helps me sort out all the alternative flows in a use case and ensure that I haven't forgotten how any of them rejoins the basic flow"

"As a notational convention, I add notes to the activity diagram at those points where the use case is extended or included. If the modeling tool you use supports the inclusion of hyperlinks to other diagrams, I highly recommend hyperlinking these notes to the relevant activity diagram to make it easier for the reader to follow the flow through all the related use cases."


Jim Conallen, Building Web Applications with UML Second Edition , ISBN: 0-201-73038-3