Re: Blank nodes must DIE! [ was Re: Blank nodes semantics - existential variables?]

On 17/07/2020 01:49, Patrick J Hayes wrote:
>
>
>> On Jul 16, 2020, at 10:29 AM, Dan Brickley <danbri@danbri.org 
>> <mailto:danbri@danbri.org>> wrote:
>>
>> On Thu, 16 Jul 2020 at 15:43, Patrick J Hayes <phayes@ihmc.us 
>> <mailto:phayes@ihmc.us>> wrote:
>>
>>     I just noticed that Dan already said this in his email. Sorry,
>>     Dan, but +1.
>>
>>
>> Let's talk it through.
>>
>> In normal RDF, the marketplace of structures you can use to make 
>> statements operate at a painfully fine-grained level, triple by 
>> triple you can draw upon types and properties that are already in 
>> use, as well as URIs standing for the things being described.
>
> Well, one person’s pain, etc.. But yes.
>>
>> In a "ShapedRDF" data format (and database?) there would be chunks 
>> that (could/should/must) correspond to shapes defined in 
>> SHACL/ShEx/etc., and which ...
>>
>>  -in the data format, a publisher would be either asserting the whole 
>> thing, or not;
>> - in a database (e.g. accessed via SPARQL) something would ensure 
>> that it was either all there, or all gone
>> - for a parser, there would be checking to not generate triples for 
>> incomplete or ill-formed shape chunks?
>
> Yes. The fact that SHACL is seen as a syntactic constraint, rather 
> than just another description, is touted as a big advantage of SHACL 
> over OWL. Sounds like just what we need here. I havnt checked the 
> details, admittedly, but the advantages of using an existing 
> recommendation outweigh any minor places of less than perfect fit.
>
> OWL/RDF parsers have been in this position, doing OWL syntax checks on 
> chunks of RDF, for over a decade. And the RDF spec does say explicitly 
> that a semantic extension can impose syntactic conditions on RDF 
> graphs (and keeping list descriptions well-formed was exactly what I 
> had in mind.)
>
>>
>> Something like RDFStar or Property Graphs could allow the shapes to 
>> be explicitly indicated in concrete syntax. But maybe that isn't 
>> needed? Perhaps the shape commitments would be declared up front at 
>> the top of the file like namespaces or json-ld @context definitions?
>
> Yes. I imagine it being rather the relationship of CSS to HTML, where 
> you can put all the structural specification into a file and just 
> reference it in the RDF file header somewhere. That allows people to 
> publicly agree on formatting (just like they do now for datatyping, by 
> using the XML schema URI) but also allows communities to develop and 
> use new ideas without having to reconvene a W3C WG to develop a new 
> standard.

Yes, this was a goal of https://www.w3.org/TR/shacl/#sh-shapes-graph 
which is similar to a @context declaration in JSON-LD.

Holger