Re: ISSUE-87: Turtle file - SHACL vs RDFS vs OWL, or all?

On 11/1/2015 0:46, Karen Coyle wrote:
> Holger, I think the question is a different one -- it's not whether we 
> use RDFS or OWL, but what we want to express, and who the audience is.
>
> The turtle file that we have today implements SHACL as a validation 
> language. I would like to see a file that serves creators of SHACL 
> documents. We do have these two "halves" of SHACL -- the description 
> of desired validation, and the validation itself. While the two can be 
> combined in a single software implementation, they shouldn't HAVE to 
> be combined. I think of this as something like the difference between 
> HTML as a language and the rendering that takes place in browsers. The 
> person creating the HTML document has a different view from the 
> software rendering the document.
>
> A vocabulary for SHACL document creation would not need any abstract 
> classes.

A role of the abstract classes is to group properties together. While it 
would be possible to attach every property to, say, sh:PropertyConstraint

sh:PropertyConstraint
     can have sh:minCount
     can have sh:maxCount
     can have sh:datatype
     ...

such a flattening would lose some information, e.g. that sh:pattern and 
sh:flags belong together (with sh:flags being optional), and 
sh:qualifiedMinCount must always co-exist with sh:qualifiedValueShape. 
The abstract classes furthermore provide focused documentation about 
these combinations, contain the produced error messages and even the 
SPARQL queries - at some stage we decided that SHACL should be expressed 
in SPARQL as much as possible. This info is still useful even for human 
readers of the data model.

> I don't know enough about templates to know how such a vocabulary 
> could address named templates, so perhaps it is best that we focus 
> first only on the defined core. Whether RDFS is sufficient or whether 
> OWL functionality is needed will come out as the vocabulary is 
> developed. It looks to me like most of the properties are fairly 
> simple, and ranges are defined in the SHACL document.

Many properties such as sh:minCount are reused in multiple places, which 
makes pure rdfs:range statements insufficient to express them. These 
would either require owl:unionOf classes or owl:Restrictions.

>
> In a sense, this becomes a test of the core vocabulary - whether it 
> can be expressed as a standard vocabulary, and if not, is that a bug 
> or a feature of SHACL?

Yes, there is value in trying to model SHACL in OWL, e.g. to help OWL 
tools and users. There is also value in modeling SHACL in SHACL, e.g. to 
help SHACL tools and users.

Holger

Received on Sunday, 1 November 2015 23:47:41 UTC