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Re: Service or graph store naming.

From: Gregory Williams <greg@evilfunhouse.com>
Date: Mon, 7 Feb 2011 15:22:09 -0500
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <99B485CC-DEAC-47B1-830B-13142AC8CC90@evilfunhouse.com>
To: Chimezie Ogbuji <chimezie@gmail.com>
On Feb 7, 2011, at 2:32 PM, Chimezie Ogbuji wrote:

> On Sun, Feb 6, 2011 at 5:30 PM, Andy Seaborne
> <andy.seaborne@epimorphics.com> wrote:
>>> returns
>>> @prefix rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>  .
>>> @prefix sd:<http://www.w3.org/ns/sparql-service-description#>  .
>>> [] a sd:Service;
>>>    sd:defaultDatasetDescription<http://host/graphstore>
>>> <http://host/graphstore>  a sd:Dataset; ..snip..
> 
>> But this says:
>> 
>> http://host/graphstore a sd:Dataset ;
>> and
>> 
>> [] a sd:Service;
>> 
>> which is odd to return from Dataset HTTP Protocol service
> 
> Yes.  I guess that suggests (if we are using the SD vocabulary for
> this purpose) we should expect the URLs of the sd:Service instance
> (when retrieved from a Dataset HTTP protocol instance) to be used.  On
> that related note, I noticed the SD vocabulary has an sd:url property
> with a domain of sd:Service and a range of a URI reference.  How is
> this different from the URI of the sd:Service instance itself? I.e.,
> this seems redundant:
> 
> <http://example.com/dataset-service> a sd:Service;
>     sd:uri "http://example.com/dataset-service"^^xsd:anyURI

Oh dear. The SD document seems to have slipped into some confusion here. My recollection is that the modeling:

[] a sd:Service ; sd:url </sparql>

was done because there's not always a one to one relationship between service and endpoint url. Doing the modeling as

</sparql> a sd:Service

means that to support situations where a service is accessible through several URLs means the SD must either duplicate a lot of the triples or support sameAs reasoning.

The example RDF in the SD document uses the first modeling pattern in which the service is a blank node with a sd:url with the endpoint url. However, I realize I confused the issue with the recent addition of the conformance section that claims to require a triple of the form:

<service-URL> rdf:type sd:Service

> In the way you think about the service and the graph store, what is
> the relationship between them? Is it one-to-one? i.e.:
> 
> sd:defaultDatasetDescription a owl:FunctionalProperty

I agree with this. I can add this to the SD vocab if there's agreement.

> I think of it as a functional relationship.  From the REST view-point,
> however, I think of it in this way (using the vocabulary from my
> earlier email on this thread and from "HTTP semantics in OWL" [1]):
> 
> @prefix tag: <http://w3.org/2001/tag/awwsw/http#>.
> sd:manages
>  a owl:FunctionalProperty;
>  rdfs:subPropertyOf sd:defaultDatasetDescription;
>  rdfs:domain sd:RESTDatasetService;
>  rdfs:range GraphStore

Are you suggesting adding this to the SD vocab?

> GraphStore owl:intersectionOf ( sd:DataSet tag:Get200WildRdfSubject
> MutableWebResource )

I don't know what tag:Get200WildRdfSubject is, nor how MutableWebResource might be represented.


.greg
Received on Monday, 7 February 2011 20:22:43 GMT

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