[news.eclipse.modeling.mdt.uml2.ocl] Re: Using OCL to specify derived Re

["Kenn Hussey" <khussey@xxxxxxxxxx>]

Yes, one of the goals of the latter feature would be to enhance the UML2 
code generator to support generating code based on OCL constraints.

Kenn

"Christian W. Damus" <cdamus@xxxxxxxxxx> wrote in message 
news:ekn2fs$u47$1@xxxxxxxxxxxxxxxxxxxx
>
> Hi, Jürgen,
>
> OCL, as UML, does not distinguish between "attributes" and "references" as
> Ecore does; these are all just Properties.  Thus, "der:" constraints
> specified in OCL can derive read-only values for either of these kinds of
> properties.
>
> You can use OCL in the EMF code generation process to specify derived
> properties as described in this article:
>
> http://www.eclipse.org/articles/Article-EMF-Codegen-with-OCL/article.html
>
> There are also plans for the UML2 UML and OCL components to implement
> support for specifying OCL constraints such as property derivations in UML
> models:
>
> https://bugs.eclipse.org/bugs/show_bug.cgi?id=163808
> https://bugs.eclipse.org/bugs/show_bug.cgi?id=105199
>
> I am not sure whether the latter item is intended to support generating 
> code
> from the OCL constraints, as in the article or otherwise.
>
> Cheers,
>
> Christian
>
>
> JG wrote:
>
>> Hi all,
>>
>> I am using Rose/Ecore to model my application models (for the
>> representation of database metadata). I have a number of a
>> Associations/EReferences whose members are actually a subset of another
>> Association. For example, a Schema contains among other things tables
>> and structured types (which are both subclasses of ModelElement). I have
>> a "content" reference from schema which can contain both of these (via
>> the common superclass). But I also want specific references like
>> "tables" and "structuredTypes" in the Schema class, which only contain
>> the tables and structured types, respectively.
>> Of course I could always write my own getters and setters into the
>> generated code that would use the "content" relationship and filter only
>> those classes that are needed. But I am hesitant to do so, as this would
>> mean a lot of effort and would make it more difficult to keep my still
>> evolving model in sync with the code.
>> I considered adding annotations and modify the way EMF generates its
>> code (so that EMF creates the getters and setters for these "derived"
>> references for me), but when I took a look at the EMF codegen templates
>> I lost my courage, as they are quite hard to read, and I did not want to
>> invest effort in modify the EMF 2.2 templates and have to do the
>> modification again for the next version of EMF that might change these
>> templates.
>>
>> My current "solution" is to have these derived references redundantly,
>> and setting them via a Helper class. For example, I have an
>> "attachTableToSchema method, which adds the given table both to the
>> "content" and to the "tables" relationship. This is however, quite
>> cumbersome and was only intended as a temporary fix.
>>
>> So to come to the question: I understand that OCL can (or is meant to be
>> able to?) specify derived attributes. Could this mechanism also be used
>> to specify a derived relationship (which is usually many-valued).
>>
>> Regards
>>
>> Jürgen
>