Re: shapes-ISSUE-104 (Union ranges): Should sh:datatype and sh:class have better support for OR? [SHACL Spec]

Holger,

The way this was handled in OSLC was to allowed multiple values for
oslc:range, which is like sh:class here. The semantics was UNION of
the classes which is the same as your proposed Or. Why not simply
allow a multiple-valued property, or a List if you really want to
stick with single-valued properties?

-- Arthur

On Fri, Oct 23, 2015 at 1:11 AM, RDF Data Shapes Working Group Issue
Tracker <sysbot+tracker@w3.org> wrote:
> shapes-ISSUE-104 (Union ranges): Should sh:datatype and sh:class have better support for OR? [SHACL Spec]
>
> http://www.w3.org/2014/data-shapes/track/issues/104
>
> Raised by: Holger Knublauch
> On product: SHACL Spec
>
> While playing with SHACL in practice, I noticed a gap in the spec.
>
> It is quite common to have properties that can take multiple types of values.  sh:text is one example where we hard-coded the pattern rdf:langString OR xsd:string, but a similar variation is xsd:date OR xsd:dateTime. Another example is skos:member, which is skos:Concept OR skos:Collection. schema.org is full of such examples.
>
> To express such unions, the current syntax is very verbose and not suitable for static analysis:
>
> ex:MyShape
>     sh:property [
>         sh:predicate ex:property ;
>         sh:maxCount 1 ;
>     ] ;
>     sh:constraint [
>         sh:or (
>             [
>                 sh:property [
>                     sh:predicate ex:property ;
>                     sh:datatype xsd:string ;
>                 ]
>             ]
>             [
>                 sh:property [
>                     sh:predicate ex:property ;
>                     sh:datatype rdf:langString ;
>                 ]
>             ]
>         )
>     ] .
>
> An option would be to use OWL's unionOf:
>
> ex:MyShape
>     sh:property [
>         sh:predicate ex:property ;
>         sh:maxCount 1 ;
>         sh:datatype [
>             a owl:Class ;
>             owl:unionOf ( xsd:string rdf:langString )
>         ]
>     ] .
>
> which is much better because it allows us to put everything into a single sh:property node. However, it adds a dependency on OWL, setting wrong expectations about inferencing and all kinds of other unsupported features such as further nested classes, NOT, AND etc, which are usually unnecessary.
>
> I believe we should support this syntax:
>
> ex:MyShape
>     sh:property [
>         sh:predicate ex:property ;
>         sh:maxCount 1 ;
>         sh:datatype ( xsd:string rdf:langString )
>     ] .
>
> In this proposal, the values of sh:datatype, sh:directType and sh:class may either be IRIs of classes or an rdf:List of IRIs. The SPARQL queries in the spec would need to be adjusted accordingly. We can delete sh:text instead.
>
> I believe this covers a large number of additional use cases while keeping the complexity and implementation burden to a minimum. I believe it is of strategic importance to have a natural way to express schema.org and other common use cases with SHACL.
>
>
>

Received on Thursday, 29 October 2015 20:22:36 UTC