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Re: shapes-ISSUE-130 (rdf dataset assumption): SHACL should not assume that the data graph is in an RDF dataset [SHACL Spec]

From: Dimitris Kontokostas <kontokostas@informatik.uni-leipzig.de>
Date: Thu, 17 Mar 2016 17:49:00 +0200
Message-ID: <CA+u4+a0M2J2kC+VVpT2z0W9YadEBESwMZnEr0fQgMwYsvHN0bw@mail.gmail.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: Holger Knublauch <holger@topquadrant.com>, Tom Johnson <johnson.tom@gmail.com>, RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
On Thu, Mar 17, 2016 at 3:20 PM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:

> The diff seems to indicate that functions still work only over datasets,
> although there is a TODO indicated.


I was waiting for Holger to wake up and clarify this but you are right


> Two "or dataset"s were also removed -
> making the dataset optional is probably benign.
>
> As far as $shapesGraph goes, wording along the lines of "can be used to
> access
> the shapes graph" would seem to work, but would need some explanation along
> the lines of "If the shapes graph is a named graph in the same dataset as
> the
> data graph then it can be accessed using its name in the dataset.
> Otherwise a
> SHACL engine would need to provide an alternative way to access the shapes
> graph."
>

tried to fix all your comments in a second commit here
https://github.com/w3c/data-shapes/commit/a0a52a4472d807683abf7cf104079f35272f27df


this is a merge of both commits but also includes a few other editorial
fixes
https://github.com/w3c/data-shapes/compare/editorial-dk

apologies for sending commits but I am not yet comfortable to commit to the
main branch

Best,
Dimitris



>
>
> peter
>
>
> On 03/17/2016 02:04 AM, Dimitris Kontokostas wrote:
> > I removed all mentions of dataset in the text that imply that validation
> works
> > on RDF datasets
> >
> https://github.com/w3c/data-shapes/commit/fa2d99fd61a473d14eef9cee57c0db1c61e03684
> >
> > One thing left to decide and close this issue  is how to refer to the
> > '$shapesGraph" variable. right now we have variations of the following
> in the spec
> > "$shapesGraph ... a named graph IRI that contains the the shapes graph"
> >
> > reading the sparql spec, named graphs imply an RDF dataset:
> > https://www.w3.org/TR/sparql11-query/#namedGraphs
> >
> > even if we remove the "named" and refer to them as just graphs, SPARQL
> uses
> > the "GRAPH" keyword in the "Querying the Dataset" section
> > https://www.w3.org/TR/sparql11-query/#queryDataset
> >
> > so, do we still have an implicit assumption that validation works on RDF
> datasets?
> >
> > Since we already have a resolution on $shapesGraph I see the following
> options:
> > a) we accept the edits as they are now in the spec and close this issue
> > b) we try to weaken further the connection and change occurrences of
> "named
> > graph" to "graph"
> > c) since this is  sparql-specific issue, we can add a disclaimer in
> section 1.2
> >
> > regarding how a SHACL validation engine wraps graphs to perform
> validation, it
> > can be an implementation detail
> >
> > Dimitris
> >
> >
> > On Wed, Mar 9, 2016 at 9:35 AM, Holger Knublauch <holger@topquadrant.com
> > <mailto:holger@topquadrant.com>> wrote:
> >
> >     Yes, you may have a point there - in cases like the default graph we
> need
> >     to make sure that the system knows which subject to look for the
> >     sh:shapesGraph triples. This is probably just a URI parameter.
> >
> >     (There are so many edit suggestions open right now that I am looking
> >     forward to sharing the workload with a second editor, now that
> Arthur has
> >     left; yes I have a day job too.)
> >
> >     Holger
> >
> >
> >     On 8/03/2016 11:02, Tom Johnson wrote:
> >>     > An RDF dataset is a purely conceptual entity. Many APIs implement
> >>     Dataset. Any Graph can be wrapped into a Dataset for execution,
> even if
> >>     that Dataset is just virtual and only has a single graph in it.
> >>
> >>     Reading the quoted text, this doesn't seem to hold. The "data graph"
> >>     links to the "shapes graph" via a triple with its graph name as the
> >>     subject. Many graphs do not have such a name (even those that are
> within
> >>     Datasets; i.e. default graphs).
> >>
> >>     Does SHACL provide a mechanism for connecting such a graph to a
> shapes
> >>     graph? If not, how does wrapping the graph in a dataset within the
> >>     implementation help a SHACL user make this connection?
> >>
> >>     - Tom
> >>
> >>     On Mon, Mar 7, 2016 at 3:00 PM, Holger Knublauch <
> holger@topquadrant.com
> >>     <mailto:holger@topquadrant.com>> wrote:
> >>
> >>         An RDF dataset is a purely conceptual entity. Many APIs
> implement
> >>         Dataset. Any Graph can be wrapped into a Dataset for execution,
> even
> >>         if that Dataset is just virtual and only has a single graph in
> it.
> >>
> >>         Holger
> >>
> >>
> >>
> >>         On 8/03/2016 2:45, RDF Data Shapes Working Group Issue Tracker
> wrote:
> >>
> >>             shapes-ISSUE-130 (rdf dataset assumption): SHACL should not
> >>             assume that the data graph is in an RDF dataset [SHACL Spec]
> >>
> >>             http://www.w3.org/2014/data-shapes/track/issues/130
> >>
> >>             Raised by: Peter Patel-Schneider
> >>             On product: SHACL Spec
> >>
> >>             """4. Declaring the Shapes Graph
> >>
> >>             A data graph MAY link to one or more shapes graphs via the
> >>             property sh:shapesGraph. The subject of this predicate must
> be
> >>             the graph resource, i.e. the name of the data graph in the
> >>             dataset. The objects of this predicate must be IRI nodes,
> >>             pointing at a named graph in the dataset. Tools may use this
> >>             information to determine which shapes graph to use for
> >>             validation. If present, tools SHOULD transitively follow any
> >>             links from the shapes graph via the predicate owl:imports to
> >>             other graphs and use the resulting union graph as parameter
> to
> >>             the validation process."""
> >>
> >>             This assumes that the data graph is in an RDF dataset.
> SHACL
> >>             validation should work on data graphs that are not in an RDF
> >>             dataset.
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>     --
> >>     -Tom Johnson
> >
> >
> >
> >
> > --
> > Dimitris Kontokostas
> > Department of Computer Science, University of Leipzig & DBpedia
> Association
> > Projects: http://dbpedia.org, http://rdfunit.aksw.org,
> > http://http://aligned-project.eu <http://aligned-project.eu/>
> > Homepage:http://aksw.org/DimitrisKontokostas
> > Research Group: AKSW/KILT http://aksw.org/Groups/KILT
> >
>
>


-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig & DBpedia Association
Projects: http://dbpedia.org, http://rdfunit.aksw.org, http://
http://aligned-project.eu
Homepage:http://aksw.org/DimitrisKontokostas
Research Group: AKSW/KILT http://aksw.org/Groups/KILT
Received on Thursday, 17 March 2016 15:49:55 UTC

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