I believe that Jacobson's statement about generalization is pre-UML 1.3
which changed the definition of use-case generalization. A good discussion
about the old and new definitions can be found in Chapter 12 of Advanced Use
Case Modeling.
Sincerely,
James.
-----Original Message-----
From: Brian G. Lyons [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, March 21, 2001 6:44 PM
To: Williamson, Rusty; 'Rose Forum'
Subject: RE: (ROSE) UML question number one
hiho,
> Does anyone know if there is any kind of requirement that use cases in
> extent and include relationships must always be abstract use cases?
There is no actual requirement that I can find. While it would be most
common for the included use case and the extension use case to be abstract,
there is no constraint along these lines in the UML metamodel. Furthermore,
there is no such constraint with respect to use-case generalization. I
actually couldn't find a reference in the official UML 1.3 specification to
abstract use cases; it can just be inferred based on the fact that in the
underlying metamodel a UseCase is a child of Classifier which is a child of
GeneralizableElement which can be abstract.
On the other hand, the UML Reference Manual by Rumbaugh et al clearly states
"Note that the extension use case is not to be instantiated, the base use
case must be instantiated to obtain the combined base-plus-extensions
behavior" (p490).
With respect to Generalization, Jacobson makes some allusions on the topic
in The Unified Software Development Process text. He states that
"generalization is employed to simplify the work with and the understanding
of the use-case model and to reuse 'semimanufactured' use cases when putting
together complete use cases requested by customers. Such complete use cases
are called concrete use cases... The 'semimanufactured' use cases exist only
for other use cases to reuse and are known as abstract use cases" (p168).
So he is *implying* that the base use case in a generalization realization
is expected to be abstract... but I'm not sure he is saying it must always
be abstract.
Than Jacobson describes a lot of circumstances that would lead one to
believe that it is most typical that included and extension use cases are
abstract. But I can't see that he makes it mandatory.
------ b
--
Brian G. Lyons
Number Six Software - Voted Rational's Best Complementary Service Provider
1655 North Fort Myer Drive, Suite 1100
Arlington, VA 22209-3196
http://www.numbersix.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Williamson, Rusty
Sent: Wednesday, March 21, 2001 1:14 PM
To: 'Rose Forum'
Subject: (ROSE) UML question number one
Hello,
Does anyone know if there is any kind of requirement that use cases in
extent and include relationships must always be abstract use cases?
Thanks!
Rusty
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Rusty Williamson
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