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TopQuadrant's position on RDF Shapes working group

From: Holger Knublauch <holger@topquadrant.com>
Date: Tue, 22 Jul 2014 13:22:05 +1000
Message-ID: <53CDD8DD.6000404@topquadrant.com>
To: public-rdf-shapes@w3.org
This is to clarify TopQuadrant's position with regards to this working 
group and its charter.

We believe that the topic of defining structural constraints on RDF 
graphs is an important issue that we and our customers have encountered 
in many real-world use cases. TopQuadrant would like to join and 
actively contribute to this working group. We have also started to 
contact users of SPIN to see who else may want to join us with our efforts.

Our preference is that the starting point of this working group should 
be SPIN, and our goal will be to collaborate with the other group 
members to upgrade a sub-set of the current SPIN specification to become 
the standard recommendation on constraint checking. We do not support 
the introduction of yet another language such as ShEx and will continue 
to strongly argue against it. Many previous emails have detailed 
concerns shared by others.

Specifically (and I haven't worked out the details), we could propose a 
sub-set of SPIN consisting of the property spin:constraint that is used 
to link OWL/RDFS class definitions with SPARQL CONSTRUCT or ASK queries 
that deliver constraint violations, and to allow the use and definition 
of SPIN templates. The standard would include a library of standard 
templates that would cover the most frequently needed use cases 
(including minimum/maximum cardinality etc). This template library would 
make it possible to cover a wide range of use cases in a declarative RDF 
vocabulary, even for people who do not know SPARQL. However, we believe 
it is important to have the "escape mechanism" allowing the inclusion of 
SPARQL queries directly. The exact scope (e.g. whether the SPIN RDF 
syntax would be included) of the submission needs to be worked out and I 
can see arguments going both ways.

If the working group decides that SPIN is not the right starting point, 
then our next best proposal is to make something like StarDog ICV the 
standard. This would have a key advantage that the "restrictions" 
defined for many OWL ontologies already exist. Indeed, the absence of 
intuitive closed-world semantics has been a major obstacle to wider 
adoption of OWL, and it would be a great outcome if an OWL extension 
would be standardized that allows to repurpose existing work and tooling 
for constraint checking. Besides, Manchester Syntax may be a good 
starting point for a human-readable syntax.

If this WG focuses on defining closed-world semantics for OWL, then we 
consider to open a completely new working group for the whole SPIN 
specification (including SPIN rules), if there is enough interest. OWL 
and SPIN can happily be used together, and in fact we have SPIN 
libraries that use OWL declarations and execute them as constraints. 
SPIN would remain the best choice for cases where the expressivity of 
OWL is not sufficient.

Regards
Holger (on behalf of TopQuadrant)
Received on Tuesday, 22 July 2014 03:22:39 UTC

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