Re: using Shape Expressions to validate RDF graphs

On 07/11/2014 02:32 PM, Karen Coyle wrote:
>
>
> On 7/11/14, 12:56 PM, Peter F. Patel-Schneider wrote:
>> I'm still trying to figure out how shape expressions can constrain the
>> shape of RDF graphs.  Yes, they can constrain the shape of a RDF graph
>> flowing out of a single source, but that's only part of the problem.
>> Another part, and one that I think is much more important, is
>> constraining the "shape" of nodes that belong to a particular class.
>
> Classes are orthogonal to shapes -- classes are semantic, shapes are
> syntactic. The Description Set Profile [1], which was an XML schema model for
> creating shapes with RDF, tried to address that (and I think it's worth
> looking at). That project was perhaps premature and never completed, but I am
> still convinced that the need to define the shape of our data exists.

Sure, but the first thing that I want to do is to check whether nodes that 
have rdf:type links to :Person also have :spouse links and that spouse has a 
type link to :Person.  If you don't like rdf:type links then use some other 
link there, but the idea is still the same - I want to know whether the nodes 
that I care about (nodes with type :person, nodes with a :university) link, 
...) have a particular "shape".  Of course, I *also* want to have more complex 
conditions, like nodes that have an rdf:type link to :Person in the RDFS 
closure of the graph, but something that can't even do the first part of this 
don't seem very useful to me, except in one-to-one situations and maybe not 
even then.

> And
> shaping - as the DSP does - requires a big picture of your data. Much
> validation looks at individual "bits" but there is also a need to formulate
> and test large, complex structures, in addition to individual statements. If
> this capability does not exist in ShEx then we need to add it.

Agreed.

>
> kc
> [1] http://dublincore.org/documents/dc-dsp/

peter