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Re: RDF Data Cube validator. Problem with one integrity constraint: IC-12

From: Dave Reynolds <dave.e.reynolds@gmail.com>
Date: Tue, 16 Jul 2013 16:46:53 +0100
Message-ID: <51E56AED.5040203@gmail.com>
To: Jose Emilio Labra Gayo <jelabra@gmail.com>
CC: public-gld-comments@w3.org
Hi Jose,

Finally found time to look at this, sorry for the delay.

Short answer:

The data is incorrect (or at least incomplete) but in ways that the 
official integrity checks don't spot. The on line tool does use a 
different implementation of IC-12 (to avoid the scaling problem with the 
sparql query) that accidentally picks up the problem.

Details:

You have a number of qb:Observations which say they are in the data set 
dataset:Computation.

However dataset:Computation is not defined anywhere and in particular 
does not have an associated qb:structure.

The rule IC-12 checks for duplicate observations for which the value of 
every declared dimension is the same. In the case where no dimensions 
are apparently declared the official IC-12 SPARQL query will pass by 
default because it never finds any duplicate observation values. The 
hand coded more efficient version in the validator sees multiple 
observations in the same data set which don't differ by any dimensions. 
Essentially a difference how the null case is treated.

This does reveal a limitation of the integrity checks.

The rules check that every qb:Observation has a qb:dataSet value and 
that every declared qb:DataSet has a qb:structure but doesn't catch the 
case where there a qb:DataSet is implicitly used but not declared. That 
is a limitation of the simplified closure algorithm.

The WG will need to consider what to do about that.

Thanks for the report.

Dave

On 08/07/13 13:34, Jose Emilio Labra Gayo wrote:
> I have a running example that I am trying to validate with the RDF
> Data Cube validator.
>
> Using my local copy of the queries it passes all the tests, however,
> when I try to use the RDF Data Cube Validator, it fails for integrity
> constraint 12.
>
> I attach the file and my local copy of the query, it is the query from
> the specification plus the prefixes and it returns NO (=success).
>
> Is it possible that the validator is using a different version of the
> query which makes it to fail?
>
> --
> Best regards, Labra
>
Received on Tuesday, 16 July 2013 15:47:23 UTC

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