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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: Mon, 21 Mar 2016 21:21:42 +0200
Message-ID: <CA+u4+a3Y5c7psmv4BYQ46LfDet+T2oDbc2cpM9ScgfqBk5BKhA@mail.gmail.com>
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: Holger Knublauch <holger@topquadrant.com>, RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
On Mon, Mar 21, 2016 at 7:56 PM, Peter F. Patel-Schneider <
pfpschneider@gmail.com> wrote:

> The spec draft currently says
>
> The definition of some constraints requires or is simplified through
> access to
> the shapes graph during query execution. SHACL validation engines MAY
> prebind
> the variable $shapesGraph to provide access to the shapes graph.
>

I wrote it that way but I placed the *requires* not for core but for the
SPARQL extension mechanism.
I thought that some complicated sparql user constraint could require access
to the shapes graph.
Isn't this one of the reason we allowed $shapesGraph? to enable some use
cases that cannot be handled otherwise?

But for me it is fine to change it to "The definition of some constraints
is simplified through access to the shapes graph during query execution..."


>
> This indicates that some constraints require access to the shapes graph
> during
> query execution.
>
> The resolution of ISSUE-47, at
> https://www.w3.org/2016/02/18-shapes-minutes.html#resolution02, indicates
> that
> access to the shapes graph during query execution is an optional feature.
> The
> SHACL spec needs to ensure that all constraints that need access to the
> shapes
> graph are optional.  The SHACL spec should go further and be very clear
> that
> access to the shapes graph is indeed optional and all all constraints that
> need access to the shapes graph are optional.
>

Right now most of the core constraint definitions use the $shapesGraph
variable,
are you suggesting that we change all these definitions or make them
optional?


>
> peter
>
>
> On 03/21/2016 04:12 AM, Dimitris Kontokostas wrote:
> > Found it, https://www.w3.org/2015/08/27-shapes-minutes.html#resolution03
> > the resolution does not say this but iirc the discussion (which is not
> 100%
> > scribed) was talking about bnodes and how they can be identified with a
> remote
> > call vs in-memory.
> > ARQ and Sesame do something clever with bnodes which is not the case for
> all
> > sparql engines but I am not trying to re-open the old issue, only trying
> to
> > close this one using that resolution
> >
> > I propose we close this issue as: SHACL does not assume that the data
> graph is
> > an RDF dataset as addressed by the current editor's draft
> > This of course allows people to use datasets but SHACL doesn't take any
> > special care in this case
> >
> >
> > On Mon, Mar 21, 2016 at 12:59 AM, Holger Knublauch <
> holger@topquadrant.com
> > <mailto:holger@topquadrant.com>> wrote:
> >
> >     On 18/03/2016 18:38, Dimitris Kontokostas wrote:
> >>
> >>     On Fri, Mar 18, 2016 at 9:41 AM, Peter F. Patel-Schneider
> >>     <<mailto:pfpschneider@gmail.com>pfpschneider@gmail.com
> >>     <mailto:pfpschneider@gmail.com>> wrote:
> >>
> >>         If it is always possible to construct the dataset, then I don't
> see
> >>         a problem
> >>         either.  However, is this always possible?  For example, a user
> who
> >>         is just
> >>         trying to validate a graph may not have permissions to create or
> >>         modify a dataset.
> >>
> >>
> >>     iirc there was a resolution on supporting only in-memory validation
> (not
> >>     my favorite and cannot find it), e.g. full shacl may not run on
> remote
> >>      datasets e.g. sparql endpoints.
> >>     With this in mind an implementation could just copy the shapes &
> data
> >>     graph in memory and perform the validation there
> >
> >     The resolution that we made a while ago was to not require support
> for the
> >     SPARQL endpoint protocol. Note that this is different from the
> question of
> >     in-memory vs database. It means that implementations can still work
> >     against databases, e.g. via an API such as ARQ or Sesame (for which
> all
> >     major databases provide drivers for), while the SPARQL endpoint
> protocol
> >     is too limiting for what SHACL needs to do.
> >
> >     Holger
> >
> >
> >
> >
> > --
> > 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 Monday, 21 March 2016 19:22:37 UTC

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