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Re: [emfindex-dev] Contributing the QVT Declarative Model Registry to EMF Index
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Ed,
just a clarification: Sven was not talking about the storage of the
index data but about the type of the index query results.
We are already providing an SPI for different storage backends, such
as CDO. As the index does not provide any more information than is
stored in the models, I expect a CDO implementation not to actually
store any additional index data, but map the index queries instead and
transform the result into descriptors.
Regards
Jan
Am 07.08.2009 um 14:57 schrieb Ed Merks:
Sven,
A model-based index backed by CDO might be pretty interesting in
that it could scale to massive instances. I'm not sure if Eike is
following this mailing list, so I've CC'd him..
Sven Efftinge wrote:
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
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