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Why save all resources in DAnalysisSession [message #1790079]

Mon, 04 June 2018 08:54

Eclipse User

Hi,

I'm analyzing sirius models saving performance. In my test scenario, i have a model with many representations, i extract each representation to a separated .aird file, then analyze the saving process.
I found that when i edit in a diagram, than save it, the system will save all aird files in the same session.
When i analyze the source codes, i found in DAnalysisSessionImpl.doSave() function, it add all session resources, semantic resources and controlled resources to a set, then get a saving policy (IsModifiedSavingPolicy) to save these resources. In IsModifiedSavingPolicy, it compute which resource need to do save, in its filter, it get resources which has been logically modified, and get resources which references to the logically modified resources.

For example, resource A is logically modified, resource B and C are not changed, but B and C reference to A, so it save all A, B and C.

Is there any reason to save B and C? I want to comment out save B and C, but i'm afraid it bring some mistakes.

Re: Why save all resources in DAnalysisSession [message #1790082 is a reply to message #1790079]

Mon, 04 June 2018 09:25

Eclipse User

Hi

The problem is the stability of xmi:id references. The default EMF policy is to avoid wasting space on xmi:id definitions at the expense of longer xmi:idref positional values that obviously vary if the content changes. Therefore all referring models must be saved if the referred model changes. If not, look forward to the excitements if unresolved proxies.

You may use custom EMF Resources that implement your own xmi:id policy. NB just generating explicit xmi:id values won't help since the values may still change, particularly if using UUIDs.

A solution which may be applicable is to generate semantically stable xmi:ids so that they do not change as surrounding context changes. If you really want to go down this approach look at the OCL LUSSID (Locally Unique Sementically Sensitive IDentifier) in GIT\org.eclipse.ocl\plugins\org.eclipse.ocl.pivot\src\org\eclipse\ocl\pivot\internal\resource\LUSSIDs.java.

Regards

Ed Willink

Re: Why save all resources in DAnalysisSession [message #1790128 is a reply to message #1790082]

Tue, 05 June 2018 10:44

Eclipse User

Hi Ed,

The scenario we had in mind and that may not be true anymore is the following:

- We have resources using xpath to reference its object and not ids.
- We have a model A referencing an element E in a model B in a multi EReference.
- In a diagram editor we reorder E before another element with the properties view.
- It seems at some point that the change did not flag A as modified so the save would ignore it causing problems to the next opening.

Do you see any misunderstanding?

Regards

Re: Why save all resources in DAnalysisSession [message #1790132 is a reply to message #1790128]

Tue, 05 June 2018 12:01

Eclipse User

Hi

If you are using Xpath then my comments may be totally irrelevant. But since this is the Sirius newsgroup and AFAIAA Sirius exploits EMF, which has no support for Xpath, I would expect normal EMF policies to apply to saving,.

While you might use Xpath for some references, are you sure that EMF references are not used for others.

Either way if you are saving Resources from a ResourceSet, EMF can save them all to memory, compare with the file system and only actually write those that are changed.

Regards

Ed Willink

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