Re: Why not adopt ShEx? (was Re: Enough already)

Hi Dean,
So what do you use for this work? Did you implement SHACL Full?
Thanks.
--
Arnaud  Le Hors - Senior Technical Staff Member, Open Web & Blockchain 
Technologies - IBM Cloud




From:   Dean Allemang <dallemang@workingontologist.com>
To:     "Eric Prud'hommeaux" <eric@w3.org>
Cc:     public-rdf-shapes@w3.org
Date:   12/12/2016 09:05 PM
Subject:        Re: Why not adopt ShEx? (was Re: Enough already)
Sent by:        deanallemang@gmail.com



There are three validation operations I can imagine wanting to perform
on an engine that supports SPARQL:

This is a lovely idea, but it isn't realistic from the beginning.  We are 
in the position of having a vendor work with us, with their current 
technology stack.  We can't expect them (and we don't have time to wait; 
once a PoC is approved, it is usually due yesterday) to adapt their stack 
to something new.  Of course, once we have a Recommendation in place, it 
is a lot easier for us to request compliance to it.  I am interested in a 
smooth slope to adoption.  A SPARQL based constraint system is easy to 
adopt in the current environment.  As adoption of the standard progresses, 
adherence to acceptance criteria will be a good idea (and we would be 
interested in cooperating in developing those)

  3 Extend the SPARQL engine to support SHACL Full's extensibility
    mechanism.

I find this criterion to be particularly interesting.  As a standards 
organization ourselves, I don't think we are in a position to make use of 
this (are we going to publish our own extensions to SHACL? I don't think 
so).  But from an implementation point of view, this is really awesome.   
I don't know that we would need to have candidate POC vendors pass this 
one.

Dean





On Mon, Dec 12, 2016 at 2:48 PM, Eric Prud'hommeaux <eric@w3.org> wrote:
* Dean Allemang <dallemang@workingontologist.com> [2016-12-12 10:33-0500]
> >
> > Sorry, but I see zero advantages of ShEx over SPIN/SPARQL.
> >
> > Why would I want to lock my software into a new non-standard syntax 
with
> > close to none adoption, when I can simply use the query engine to 
validate
> > constraints?
> >
> >
> >
>
> I couldn't agree more.  In FIBO,  we have been looking for a constraint
> language to help us make definitions that go beyond the capabilities of
> OWL.  I presented these at the inaugural meeting of the SHAPES group a
> couple years ago.  It is easy to specify them in SPARQL, and we have 
done
> so (and I did the same in SHACL, now that there is a write-up of how it
> works).
>
> When we move from our conceptual ontology to something operational for a
> Proof of Concept, some vendor is always  involved.  That vendor 
(different
> one for each PoC) always has an RDF store somewhere in their stack.  
They
> can always consume OWL (though often through a rule engine 
interpretations
> via OWL2RL).  For rules/constraints that go beyond OWL, we have to work 
out
> some way to give them the rules.   SWRL?  Some of them can manage that.
> RIF?  Everyone knows what it is, but few can handle it out of the box.
> Other rule systems have varying degrees of uptake.
>
> But one thing all the triple stores can manage is SPARQL.  "How about if 
I
> give you the constraints in SPARQL?"  the answer is always, "Oh, sure, 
that
> works".  Because they are all triple stores, and they already do it.

There are three validation operations I can imagine wanting to perform
on an engine that supports SPARQL:

  1 Validate ShEx or SHACL core over a the SPARQL protocol.

  2 Validate ShEx or SHACL core over a graph API.

  3 Extend the SPARQL engine to support SHACL Full's extensibility
    mechanism.

For 1 and 2, I think ShEx and SHACL are about equal. Peter's
implementation of SHACL Core used a mixture of graph API and SPARQL
but could certainly have been implemented just in terms of the
ubiquitous triplesMatching API. The ShEx demo compiles ShEx 1 to
SPARQL queries to run over the SPARQL protocol but of course that
didn't support features like told bnodes (identifying a bnode by
label).

I think SPARQL becomes relevent when you want to build a SHACL Full
(or SPIN) engine. You would have to implement a full SPARQL engine
*and then* build the node/shape iterators, templating system, and
recursion control that are required for SHACL Full.


> This doesn't mean that we have to do this in SPARQL, but it does mean 
that
> if we have that option, we shortcut a lot of work to get to our Proofs 
of
> Concept.
>
> In the end, I'm just re-iterating what Martynas has said much more
> succinctly, but in the context of a whole industry effort (FIBO) and a
> selection of vendors who want to work with us.
>
>
>
> Dean

--
-ericP

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