Re: Early feedback on SHACL Spec appreciated

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Right now the specification is quite incoherent.

There is Section 2, which appears to define a language.  However, this
definition does not appear to be used anywhere else in the document.  As far
as I can tell the SPARQL definitions later in the document do not conform to
the definitions in this section.

The introduction talks about constraints being attached to shapes.  What
does this mean?  The introduction talks about restricting the predicates of
triples.  What does this mean?  The introduction talks about SPARQL a lot.
In general I found the introduction to be more confusing than descriptive.

There are many aspects of the described SHAQL that are not supported by
resolutions of the working group, such as:
- - the division of constraints into native and template constraints
- - the use of a native executable
- - the use of SPARQL as the native executable
- - template shapes
- - private shapes
- - specialization of shapes
- - abstract shapes
- - final shapes
- - matching of literals instead of their values
- - contexts

The idea of having three properties that do the same thing (sh:constraint,
sh:property, and sh:inverseProperty) is not useful.  The grouping of
constraints related to the same property is not something that needs to be
recommended.  Overloading rdfs:label and rdfs:comment is not useful.

The language only allows conjunctions of primitive constraints, i.e., no
disjunction.

The supported operations don't make sense.  How can a single constraint be
checked without some notion of what graph or dataset is involved, and what
scope is involved for constraints that need a scope?


I don't view this document as a useful step forward.

peter





On 02/26/2015 03:34 PM, Holger Knublauch wrote:
> Hi all,
> 
> in the F2F today, I mentioned that the current draft of the Spec
> 
> https://w3c.github.io/data-shapes/data-shapes-core
> 
> may now be ready for a first round of feedback. Needless to say it is
> early, has unfinished places (marked in red) and definitions may not be
> precise enough yet for those who love to drill into such details. All
> this needs fixing over the coming year.
> 
> Yet, Arnaud indicated that we should aim at producing some First Public 
> Working Draft soon, and *we have to start somewhere*, so I am exposing
> the current draft now in its raw form.
> 
> Compared to the Primers, I hope I have addressed some issues: - We now
> use sh:Shape consistently - Controversial issues about
> rdf:type/sh:nodeShape are marked as controversial - SPARQL is now more
> clearly separated into its own native language mechanism - There is no
> "OO" or "Modeling" story line - it's just a plain language spec.
> 
> Regard this document as a "SHACL Full". We should probably also create
> another deliverable for a lighter sub-set of SHACL, especially for those
> who prefer formal abstract definitions of the core language and worry
> about expressivity or complexity in general. This should be perfectly
> doable via sh:Profiles.
> 
> I will continue to add bits here and there, this is still work in
> progress. Yet I would appreciate feedback (even on details), so that we
> can determine how far away we are from a FPWD. I will mark sections that
> have received substantial comments in the document (and we can open red
> Issue blocks for the time being).
> 
> Many thanks Holger
> 
> 
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Received on Friday, 27 February 2015 06:03:57 UTC