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Re: [emfindex-dev] Contributing the QVT Declarative Model Registry to EMF Index

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?



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).



The GUI supports maintenance of registrations using a Property Page.

All the GUI stuff is still missing.

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.


Regards,
Sven