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Re: ISSUE-95 Discussions

From: Holger Knublauch <holger@topquadrant.com>
Date: Fri, 29 Jan 2016 14:45:15 +1000
To: "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
Message-ID: <56AAEE5B.9070408@topquadrant.com>
On 29/01/2016 3:34 AM, Arthur Ryman wrote:
> Holger & WG,
>
> One of the principles of good RDF design is to treat URIs as opaque.
> That means applications should not assume that a URI conforms to any
> given pattern. In principle the URI of an ontology could be completely
> unrelated to the URIs of its terms. We all probably think that is a
> terrible thing to do, but RDF seems to strive towards accommodating
> any conceivable way of working. Therefore we should always be explicit
> about the relation between a term and its defining ontology, hence the
> presence of the explicit rdfs:isDefinedBy triples.
>
> The use of explicit rdfs:isDefinedBy triples also allows you to easily
> split up a large vocabulary into multiple graphs. This decouples the
> vocabulary from how it is stored in graphs. Furthermore, it
> distinguishes vocabulary terms from other resources that might be
> present in a given graph. In effect, we are treating all subjects of
> rdfs:isDefinedBy as vocabulary terms. This is handy for individual
> terms defined by a vocabulary, i.e. terms that are neither classes nor
> properties.

The latter paragraph has convinced me :) We will have at least two files 
on the web: the RDFS vocabulary and a SHACL file extending the 
vocabulary with a more detailed "schema" to validate SHACL files. I 
suggest that each resource gets two rdfs:isDefinedBy triples, pointing 
to both files so that tools can discover the SHACL definitions too.

>
> The use of hash URIs is one of the W3C recommended best practices for
> publishing RDF [1]. It is therefore convenient to make the URI of the
> ontology end with a hash. This is simply a convention that several
> prominent W3C vocabularies use.
>
> [1] https://www.w3.org/TR/swbp-vocab-pub/

The reference [1] above points at SKOS as the flagship example:

     https://www.w3.org/TR/swbp-vocab-pub/#hash

But SKOS uses the pattern that I also promote:

     The URI for the SKOS Core Vocabulary itself is:

|http://www.w3.org/2004/02/skos/core|

and if you look at the Turtle from

http://www.w3.org/TR/skos-reference/skos.rdf

   <owl:Ontology rdf:about="http://www.w3.org/2004/02/skos/core">
     <dct:title xml:lang="en">SKOS Vocabulary</dct:title>
...

No # at the end. All owl:imports to SKOS also point at the URI without #.

Do you have a (normative) reference that owl:Ontologies should end with 
#? I otherwise suggest removing the # because that practice seems to be 
more widely used (the RDF namespace itself being the main exception).

Thanks,
Holger
Received on Friday, 29 January 2016 04:45:56 UTC

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