Skip to main content

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [List Home]
Re: [emfindex-dev] Contributing the QVT Declarative Model Registry to EMF Index

Hi Sven
Hi Ed,

Jan (the project lead) is currently trying to collect all kinds of requirement in order to overwork the current API and implementation a bit. So it seems that now is a good time to make sure that your requirements are supported.

I've put my thoughts inlined...

Tool support for OCL or QVTc or QVTr must perform a two level model name resolution.

a) name to nominal URI
b) nominal URI to precise URI

In OCL a package context specifies a package name without specifying where that package may be located. In QVTc or QVTr a transformation references a meta-model name again without specifying where that meta-model may be located.

The (originally UMLX) QVT Declarative Model Registry supports a) and b) by prioviding a per-project set of registrations that are scoped by resources (File or IResource), allowing a user to provide registrations with project, folder or file granularity. Registrations are defined for a chosen Model Accessor namespace, so that Model Name registrations map from ad hoc name such as myUML to nominal URI such http://my.uml, and URI registrations map from nominal URI to precise URI e.g. platform://resources/myuml/model/uml.ecore.

There is no nominal to precise URI mapping in our current implementation.
Could you please outline the use-case, so we can discuss this feature further?
I am sure that half the nominal-URI to precise-URI functionality is already because there are two use cases. I want to resolve a nominal URI to a precise URI that is needed for getResource to succeed.

a) The precise URI is a registered EMF model. I think Ecore can now register the .ecore, though in the past my enhanced Browse Workspace... deduced .ecore as siblings of .genmodel.

b) The precise URI is my own meta-model whose existence is solely an .ecore file in my current workspace. EMF does not support this use of non-Java genmodelled models, for which no plugin registration can occur.

Arguably what I require for the above is just a modeling-time user configurable URI resolver.

The model-name:nominal-uri resolver is just a generalisation to support multiple resolution domains that I called Model Accessors.


The Model Name accessors are completely user defined.
The URI accessors enhance the built-in EPackage.Registry resolutions with user defined mappings for models that need not be reified as Java code.

The registry is persisted as an EMF model in .settings/org.eclipse.qvt.declarative.modelregistry

The model in the current implementation is not backed-up by EMF implementation. I think it would be good to have plain Java interfaces as API, leaving it to the implementation whether you want to implement the model with EMF. Jan mentioned that he likes the idea of having an EMF model, because maintaining crossrefs and state would be easier because of the observer pattern (adapters) and the managed references. On the other hand I can imagine that people might want to have a very lazy model, that is implementing it with proxies (I don't mean EMF proxies).

Perhaps I should leave this discussion to the team. Perhaps I can observe that it is odd for a modelling project not to use a model for its public data API.

How can I write a transformation that uses the registry as input or output if there is no UML/EMOF/Ecore/... meta-model for it?

From a configuration management point of view I find it very unsatisfactory for project-specific registrations to be persisted anywhere other than within the project tree; i.e. somewhere in .settings. How else do I check the registrations into CVS so that my colleague shares them?
The GUI supports  maintenance of registrations  using a Property Page.

All the GUI stuff is still missing.
Perhaps my stuff may provide a bootstrap.

The API supports locating registrations and/or loading a resolution.

This functionality seems mostly complementary to EMF Index, so it seems desirable to revise the current Model Registry code so that it can be contributed to EMF Index. This will avoid migrating the QVT Declarative Model Registry to MDT OCL as would be required to support the migration of the OCL editor.

I guess that you'll have to do some kind of migration, because there is already API and code. But as I said initially you should look at the current code and try to find out what's missing in order to support your use cases.

I'm not worried whether my code is used or not. I just need the model-name:nominal-URI and nominal-URI:precise-URI mapping to be available in configurable form for MDT/OCL and M2M/QVT Declarative for Helios and I hope that we can provide a neutral solution that supports all modeling projects so that users can solve all their model registration problems in a single place rather than in a different way for each tool.

I looked at the code and it appeared that I could write my own Indexer that could exploit some of the EMF Index APIs. However if it's my own Indexer, I just trade one set of custom classes for another with an extra dependency, so why bother? It is only if there is a standard EMF Index Indexer that I succeed in sharing my functionality. I think EMF Index needs to provide abstract APIs and a concrete extensible implementation that hopefully satisfies basic model reference resolution requirements.

So what I think is missing: [a prototype is available for a), b), c)]

a) A registry that is persisted as a model within the project
b) A registry information model that supports user defined registrations
c) A GUI to maintain that information model
d) [Refinement of the existing EMF Index API to support the refined registry.]

NB. My current interests are solely in Resource and EPackage resolution and loading from vague names, which is a complementary but different problem to finer grained queries within resolved models.

   Regards

      Ed Willink



Back to the top