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Re: [incquery-dev] space-time continuum breached
Sorry, I was looking at the wrong example.

Yes, the mostPopularBookCategory can return multiple matches (if there are multiple categories with equal number of books). That way, libraryName can have multiple matches as well. That _will_ break havoc obviously.

See: http://wiki.eclipse.org/index.php?title=EMFIncQuery/UserDocumentation/Query_Based_Features#Multiple_results_for_a_query_used_in_a_single_.28upper_bound_.3D_1.29_feature

I plan to extend the QBF implementation in the future to handle such issues better, but that means defining default behaviour for what should happen in these cases (which match to omit, which value to use, how to ensure that there is at least one value, etc.), which is not trivial and messes up the code.

Cheers,
  Ábel Hegedüs

Fault Tolerant Systems Research Group
Department of Measurement and Information Systems
Budapest University of Technology and Economics

On 2013.10.24. 10:24:25, Tamas Szabo <tamas.szabo@xxxxxxxxx> wrote:

No, I meant the Library.name. Have you updated the example project? I am talking about library.domain.base.
If I define the mostPopularBookCategory in the Library class (which doesn't use eval) then I frequently see that the feature has no value.
Hi,

I assume you mean Writer.name, since Library.name is not a QBF. I can see that eval is used in that query, which is the first occasion that such combination is used.

The space-time continuum is breached when a single value QBF has multiple values (i.e. there is a match appearance _before_ the previous match disappears) or when a multi value QBF loses a match that has not appeared before.

I recommend you add breakpoints to the two places where such error is logged (if it occurs for multi-value QBFs as well) and look at the source and target/removed values and the contents of the refMemories.

It is possible, that eval has some weird issue that that causes multiple matches transiently. You could try the name query without the eval (say the name is always the lastName), if that behaves correctly, then my bet is on eval, though debugging may reveal a problem in the QBF implementation.

Cheers,
  Ábel Hegedüs

Fault Tolerant Systems Research Group
Department of Measurement and Information Systems
Budapest University of Technology and Economics

On 2013.10.23. 22:55:07, Tamas Szabo <tamas.szabo@xxxxxxxxx> wrote:

Hi

@Abel: When can such a thing happen with the
Single/MultiValueQueryBasedFeature?
Can you take a look at the library.domain.base example?
If you play around with the dynamic instance model you can see some
really weird values for the Library.name feature.
Sometimes it doesn't have a value, sometimes it has a wrong value...

Regards,
Tamas
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