[news.eclipse.tools.uml2] Re: Why UML2 metamodel is "flattened" ?

["Kenn Hussey" <khussey@xxxxxxxxxx>]

Antonio,

Just to be clear, the UML2 implementation of the UML specification IS in 
fact fully alligned with, and conformant to, the UML 2.1(.1) standard...

Kenn

"Antonio Carrasco Valero" <acv@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in 
message news:eh0gbv$q74$1@xxxxxxxxxxxxxxxxxxxx
> Tas, Kenn, thanks a lot for the rationale and explainations,
> fully consistent with with the reality of the problem and solutions of 
> UML2 implementation
> and indeed with comments from EdMerks and others at Eclipse Summit.
>
> - By the way, a most memorable event. Loved it!
>
>
> --- Many Objects in Memory ---
> I understand that using the composition/delegation approach to Java 
> implementation of multiple inheritance, creates more complex object 
> networks.
>
> I observe that the choice of approach (composition/delegation) is driven 
> by the need to avoid duplicating method implementations (and data slots 
> declaration) in multiple classes,
> quite an important requirement in EMF, as developers must be able to 
> customize code,
> and do it in a single place - not everywhere a certain structure or 
> behavior happens to be inherited into.
>
> But, I hope that we can find other technical solutions,
> such that fully compliant UML2 implementations can be produced,
> while preserving our investiment in current usages of UML2
> - and ironing out one or two wrinkles in the alignment between Eclipse and 
> OMG.
>
> I look forward to James work about UML2 extension.
>
>
> --- Metamodels and Profiles ---
> The rendering of Metamodels as Profiles of UML
> is a common practice since the unification at the famous OOPSLA'95,
> and mandatory in OMG standards.
> Indeed, the last non-UML-aligned submission BOCA
> (Business Object Component Architecture, 1998) was rejected,
> and the following submissions had to include (and were in fact named 
> after)
> a UML Profile rendering of their Metamodels
> (i.e. UML Profiles for CORBA, for EDOC, for EAI, and for SPEM, among 
> others).
>
> Similarly, this reflected the duality of vendor camps,
> the one partial to UML "final" (as in Java classes, not extensible) tool 
> vendors,
> and the MOF alternative.
>
> It was my understanding that OMG's UML2 effort tried to resolve both 
> problems,
> by enabling the goal of a family of UML languages,
> with enhanced interopeability by commonality of reusable semantics,
> and unequivocal adoption of MOF as the metamodelling language of choice.
>
> Today, Eclipse proves to the community at large,
> how modelling tools can be extended with new semantics and syntax,
> that become first class citizens of the tool, as the ones originally 
> shipped by the vendor.
>
>
>
> ---  ---
> In short:
> I observe that most of the audience is being driven towards
> non UML pure unrelated Domain Specific Languages
> or to Profiling mechanisms in "final" UML tools.
>
> Therefore I see no real market or user need for "final" tools,
> and that the choices made, about which approaches to enable and 
> facilitate,
> are strongly influenced by the market dominance efforts
> that Microsoft, IBM and Sun must engage themselves in,
> to better guarantee their long term success.
>
> On the other side, the community at large is now much better equipped than 
> 10 years ago,
> in a big part, thanks to these very same dominance efforts of the market 
> leaders,
> but also to many others that wanted interoperable domain specific 
> modelling.
>
> After the amount of talent I've seen since July in
> the ECDMA, JISBD and Eclipse Summit,
> it won't surprise me a bit, if somebody comes up and publish
> open source implementations of UML2 and MOF
> that are fully aligned with the standards,
> yet still righfully Eclipse.
>
> Cheers!
>
>
>
>
>
>
>
>
>
>
>
> "Tas Frangoullides" <tas.frangoullides@xxxxxxxxxxxxxxxxxx> wrote in 
> message news:egeg97$r7l$1@xxxxxxxxxxxxxxxxxxxx
>> Hi Antonio,
>>
>>
>>
>> I'm not sure I can answer all your questions but I've done some 
>> heavyweight and lightweight extensions using uml2/emf and so some of what 
>> I've learnt might be useful.
>>
>>
>>
>> Kenn once attempted to explain all the pains of retaining the 
>> hierarchical structure of UML2 in the implementation but my head 
>> overheated before I could absorb all of it. If I rememeber correctly one 
>> of the reasons the Eclipse UML2 implementation was flattened is because 
>> it produced way too many objects in memory, even for moderate sized 
>> models. I think the UML2 spec has since been updated to reflect this and 
>> the flat structure of Eclipse UML2 is compliant. Personally I think this 
>> was a good thing also because I find navigating the metamodel hard enough 
>> without having several definitions of each element, and the API would 
>> have been way more complex. Also, because the flattening is only done at 
>> the final stage of generating the implementation you don't loose any of 
>> the cherry-picking potential of the complete metamodel.
>>
>>
>>
>> If you want  you can define your meta model based on any part of the UML 
>> superstructure or infrastructure and use the UML2 Codegen to generate 
>> implementations. When I first starting learning about the UML metamodel I 
>> was very interested in the prospect of reusing the infrastructure and 
>> unmerged superstructure but in practice I've found extending complete 
>> specification produces better and more flexible results.
>>
>>
>>
>> Although profiling is still not as flexible as metamodel extensions it 
>> does have some advantages and is much improved in version 2.1 of the 
>> spec, especially compared to UML 1.x.. The big advantage is you don't 
>> have to write your own model editor and can reuse the UML diagramming 
>> capabilities of your UML tool. However, profiles are trickier to extract 
>> data out of when processing them but you can get round this by defining 
>> both a heavyweight and lightweight extension. What I've done in the past 
>> is define a nice clean metamodel (often based on UML2, at other times 
>> just an EMF model) and then defined a UML2 profile equivalent. I then 
>> implement a transformation between a profiled UML2 model an instance of 
>> my metamodel. This gives me model instances that are clean and easy to 
>> traverse without having to develop a new diagram editor. If you have 
>> diagramming requirements beyond the UML2 diagrams then you've got lots of 
>> work to do either way. If you are interested in this sort of thing then I 
>> recommend taking a look at the GMF project.
>>
>>
>>
>> Hope that is of some use,
>>
>> Tas.
>>
>>
>>
>> "Antonio Carrasco Valero" <acv@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in 
>> message news:eg8csf$2pv$1@xxxxxxxxxxxxxxxxxxxx
>>>I am trying to produce a metamodel, not a Profile
>>>  - as EMF provides such a rich metamodel implementation platform,
>>>  that is not worth to put up with the lightweight profiling approach .
>>>
>>> My well-informed customers require their language to be as integrated as 
>>> possible
>>> with the UML Family of Languages promise of UML2,
>>> and explicitly require to reuse as much reuse as possible of UML2 
>>> semantics.
>>>
>>> But, Eclipse UML2 metamodel implementation has flattened all the UML 
>>> modeling elements,
>>> - therefore, their semantics and sintax -
>>> and only offers the "leaf" specifications.
>>> For example, in UML2 (infra & supra),
>>> there are 4 (unless I missed some) Class specifications,
>>> each incorporating selected semantics and syntax.
>>>
>>> My question is:
>>>
>>> How does Eclipse UML2 implementation support the OMG (and my customer's) 
>>> requirement
>>> of facilitating a UML2 family of languages,
>>> as opposed to forcing most users to "profile" rather than metamodel ?
>>>
>>> My customer is specially sensitive to UML profiling,
>>> because of their unfulfilled expectations in UML1.x profiling with 
>>> RRose,
>>> and perceive that it is a significant risk,
>>> to expressing their semantically rich domain and technology models,
>>> instantiating profiled vainilla UML elements,
>>> rather than fully customized metamodels.
>>>
>>> How should I educate my customers about the profile-biased Eclipse UML2 
>>> implementation ?
>>>
>>> Thanks,
>>> ACV
>>>
>>>
>>>
>>>
>>
>>
>
>