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Home » Modeling » UML2 » extents in UML
extents in UML [message #476882] Fri, 25 January 2008 16:00 Go to next message
Krzysztof Kaczmarski is currently offline Krzysztof KaczmarskiFriend
Messages: 88
Registered: July 2009
Member
Hi All,

Does UML's ReadExtentAction return only instances
of a given classifier or also instances of its specializations?
I cannot find this in the specification.

Thanks in advance,
Krzysztof
Re: extents in UML [message #476891 is a reply to message #476882] Tue, 29 January 2008 12:25 Go to previous message
Eclipse UserFriend
Originally posted by: cdamus.ca.ibm.com

Hi, Krzysztof,

As I replied in the OCL newsgroup, I repeat here for the benefit (if it is
such) of the UML2 audience.

From the Semantics of Classifier metaclass in the 2.1 Superstructure:

  "A Classifier may participate in generalization relationships
   with other Classifiers. An instance of a specific Classifier
   is also an (indirect) instance of each of the general
   Classifiers."

And from the Semantics of ReadExtentAction:

  "The extent of a classifier is the set of all instances of a
   classifier that exist at any one time."

From these two statements, as long as the term "instance" means the same in
both, I conclude that the extent of a classifier includes the extents of
its specializations. i.e., the second alternative that you indicate in your
question.

HTH,

Christian


Krzysztof Kaczmarski wrote:

> Hi All,
>
> Does UML's ReadExtentAction return only instances
> of a given classifier or also instances of its specializations?
> I cannot find this in the specification.
>
> Thanks in advance,
> Krzysztof
Re: extents in UML [message #625947 is a reply to message #476882] Tue, 29 January 2008 12:25 Go to previous message
Eclipse UserFriend
Originally posted by: cdamus.ca.ibm.com

Hi, Krzysztof,

As I replied in the OCL newsgroup, I repeat here for the benefit (if it is
such) of the UML2 audience.

From the Semantics of Classifier metaclass in the 2.1 Superstructure:

  "A Classifier may participate in generalization relationships
   with other Classifiers. An instance of a specific Classifier
   is also an (indirect) instance of each of the general
   Classifiers."

And from the Semantics of ReadExtentAction:

  "The extent of a classifier is the set of all instances of a
   classifier that exist at any one time."

From these two statements, as long as the term "instance" means the same in
both, I conclude that the extent of a classifier includes the extents of
its specializations. i.e., the second alternative that you indicate in your
question.

HTH,

Christian


Krzysztof Kaczmarski wrote:

> Hi All,
>
> Does UML's ReadExtentAction return only instances
> of a given classifier or also instances of its specializations?
> I cannot find this in the specification.
>
> Thanks in advance,
> Krzysztof
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