Re: DQV, DAQ and Data Cube graphs

Hi Christophe, Jeremy and Nandana,

Thanks for your replies, and the interesting discussion.

It seems we have an agreement  on proposal 4,

Proposal 4:   define  in DQV the new class dqv:QualityDataset which
replaces daq:QualityGraph,   is defined as   subclass of qb:DataSet, but it
is not a subclass of RDFg:Graph.

In my opinion,  this should  solve ISSUE-182 :
http://www.w3.org/2013/dwbp/track/issues/182 - The label of
daq:QualityGraph does not fit well with the current model.


Reading your replies,  I think we are not far from solving   also the

ISSUE-181:  http://www.w3.org/2013/dwbp/track/issues/181 - Should we have
only the existing class daq:QualityGraph or keep the new class
dqv:QualityMetadata?

As far as I have understood, we want to keep  the class dqv:QualityMetadata,
because  we want to provide  provenance at different granularity levels,
 and that is possible because both dqv:QualityMeasure and
dqv:QualityMetadata are  prov:Entity.

Perhaps , the   missing piece is if we want to have dqv:QualityMetadata as
RDFg:Graph or not.

So we might close the issue181 deciding between the two options mentioned
 by Nandana in [1],

namely,

to keep dqv:QualityMetadata  as RDFg:Graph,

or

 to explicitly relate a set of quality measures and annotations to a
dqv:QualityMetadata using some RDF relation defined in DQV ( similar to
dqv:hasQualityMeasure or db:dataset). dqv:contains ( Domain:
dqv:QualityMetadata -> Range: [ owl:unionOf ( dqv:QualityMeasure
 dqv:QualityAnnotation) ] )
What do you think? any preference?

Regards,
 Riccardo

[1] https://lists.w3.org/Archives/Public/public-dwbp-wg/2015Sep/0003.html

On 3 September 2015 at 13:23, Debattista, Jeremy <
Jeremy.Debattista@iais.fraunhofer.de> wrote:

> Hi Antoine, Riccardo, Christophe,
>
> Sorry for my late reply but I got stuck on other things. I’ll try to group
> replies from all emails in one.
>
> (1) Compatibility between daQ and DQV
>
> If we resolve ISSUE-180 [1] by not re-using directly the DaQ elements, we
> can solve both issues at once. Here are two proposals from me:
>
> PROPOSAL 1: Replace daq:QualityGraph by a new class (say,
> dqv:QualityMeasureGraph)
> PROPOSAL 2: Drop daq:QualityGraph and represent quality measures in graphs
> of the same class as the other quality metadata (ie., graphs of type
> dqv:QualityMetadata)
>
>
> I think if dqv:QualityMetadata and daq:QualityGraph are equivalent
> classes, then both will be compatible because they will have the same set
> of individuals. Please correct me if I’m wrong.
>
> We still have the issue  of backward compatibility between DQV and DAQ. I
> guess this issue might be solved by defining   daq:QualityGraph as
>  subclass of  dqv:QualityDataset, we might discuss this with DAQ designers,
> ( @Jeremy, what do you think? Does it work?)
>
>
> I don’t think subclasses will work because instances will only be
> compatible one way (i.e DQV -> DAQ or DAQ -> DQV).
>
> Therefore, in order to keep the data cube feature without using
> rdfg:Graphs, one possible solution is as Riccardo proposed:
>
> Proposal 4:   define  in DQV the new class dqv:QualityDataset which
> replaces daq:QualityGraph,   is defined as   subclass of qb:DataSet, but it
> is not a subclass of RDFg:Graph.
>
>
> but making dqv:QualityDataset a subclass of qb:DataSet using the cube data
> structure definition defined in daQ (daq:dsd).
>
> If what I’m saying is correct, then I think it will make daQ and DQV
> compatible with each other. What do you think?
>
> On the other hand, if you think that the compatibility from DQV to daQ is
> not important, then subclassing should be enough.
>
>
> (2) Usage of rdfg:Graph in daQ and Provenance
>
> You are right,  we don't need to keep the daq:QualityGraph as a
> rdfg:Graph, but we still need a subclass of qb:DataSet as  range of the
> property  qb:dataSet
> to facilitate the visualisation of the data as RDF cube.
>
>
> The idea of storing quality metadata as graphs was in order to make a
> distinction between the data itself and the metadata. It also makes things
> easier for crawling and querying in my opinion, whilst also tracking the
> provenance of quality observations  Each daQ observation is also a prov-o
> entity [1].
> I agree that provenance at different granularity levels - as Nandana wrote
> in his reply - is required.
>
> Cheers,
> Jer
>
> [1] http://purl.org/eis/vocab/daq
>
> On 27 Aug 2015, at 01:12, Antoine Isaac <aisaac@few.vu.nl> wrote:
>
> Dear all,
>
> While preparing the last mail, Riccardo and I started a longer discussion
> on which the group's input would be welcome.
>
> This is about the following issues:
>
> http://www.w3.org/2013/dwbp/track/issues/181 - Should we have only the
> existing class daq:QualityGraph or keep the new class dqv:QualityMetadata?
> http://www.w3.org/2013/dwbp/track/issues/182 - The label of
> daq:QualityGraph does not fit well with the current model -
>
>
>
> Riccardo has pointed out that we should keep in mind also issue 191 [2]
> DaQ has been made consistent with RDF Data Cube (qb: namespace [5]):
> daq:QualityGraph is a sub-class of qb:DataSet, so that results of the
> quality measures can be visualised by RDF-cube visualizer (see [3]). This
> is very useful feature and he thinks we should preserve it in DQV. And I
> agree.
> So when dropping daq:QualityGraph, we have to think where to put the
> qb:DataSet subclassing and to the rearrange qb:dataSet property in our
> graph at [4]
>
> Riccardo suggests another (orthogonal) proposal:
>
> PROPOSAL 3: define dqv:QualityMetadata as a subclass of daq:QualityGraph.
>
> With this we keep compatibility with DaQ and Data Cube. We don't have
> nested graphs anymore - only a graph grouping together all the measures and
> annotations, and whose provenance can be easily tracked.
>
> The problem is semantics: qb:Dataset is defined as "collection of
> statistical data" and a daq:QualityGraph "contain all metadata about
> quality metrics on the dataset". So these are rather numerical
> observations, while our dqv:QualityMetadata can include more diverse
> metadata, for example textual annotations.
>
> What do you think?
>
> Best,
>
> Antoine
>
> [1] http://www.w3.org/2013/dwbp/track/issues/180
> [2] http://www.w3.org/2013/dwbp/track/issues/191
> [3] http://eis-bonn.github.io/Luzzu/papers/semantics2014.pdf
> [4] http://www.w3.org/TR/vocab-dqv/#vocabulary-overview
> [5] http://www.w3.org/TR/vocab-data-cube/
>
>
>
> --
> This message has been scanned for viruses and dangerous content by
> *E.F.A. Project* <http://www.efa-project.org>, and is believed to be
> clean.
>



-- 
----------------------------------------------------------------------------
Riccardo Albertoni
Istituto per la Matematica Applicata e Tecnologie Informatiche "Enrico
Magenes"
Consiglio Nazionale delle Ricerche
via de Marini 6 - 16149 GENOVA - ITALIA
tel. +39-010-6475624 - fax +39-010-6475660
e-mail: Riccardo.Albertoni@ge.imati.cnr.it
Skype: callto://riccardoalbertoni/
LinkedIn: http://www.linkedin.com/in/riccardoalbertoni
www: http://www.ge.imati.cnr.it/Albertoni
http://purl.oclc.org/NET/riccardoAlbertoni
FOAF:http://purl.oclc.org/NET/RiccardoAlbertoni/foaf