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Re: Dereferencing a URI vs querying a SPARQL endpoint

From: Giovanni Tummarello <g.tummarello@gmail.com>
Date: Thu, 21 May 2009 08:57:50 +0100
Message-ID: <210271540905210057y1ab12314qe6d45d30debde78@mail.gmail.com>
To: Daniel Schwabe <dschwabe@inf.puc-rio.br>
Cc: public-lod@w3.org, "semantic-web@w3.org" <semantic-web@w3.org>
Hi,

there isnt a single answer unfortunately.
Lets take symetric concise bound descriptions (SCBD) which basically
means from the uri you'll get triples around it recursively until you
find other URIs. (so when you find a blank node you keep on going).

This seems a pretty good way to provide data since it allows more than
simple "triples" attached to the subject to be returned. For example
in freebase they have datastructures that are composed by "actor,
role, movie" and that, clearly, cannot be represented in a single
triple (e.g. Sean Connery playing James Bond in GoldFinger)

 if you were to use a blanknode as the central node of this structure
(assuming nobody wants to talk directly about this structure otherwise
one could use a URI for it but then also a blank node to glue things
together) you'd be able to return it from the "sean connery"
description or the "james bond" description or the "goldfinger"
description by returing the respective SCBD.

Ok so even if this sounds like a good choice, its easy to see that in
practice this is not sufficient, e.g. james bond would be a URI with
no label if you fetch any of the other 2 nodes.

So probably a "SCBDwL" (with labels (and types) :-) ) is in fact more
like what's needed..

Giovanni




On Thu, May 21, 2009 at 12:02 AM, Daniel Schwabe
<dschwabe@inf.puc-rio.br> wrote:
> On 20/05/2009 17:14, Hugh Glaser wrote:
>>
>> Sorry, I'll try harder :-)
>> I understand that what you are asking is something like this.
>> For some sites (including rkbexplorer), when you resolve a URI, it
>> constructs a SPARQL query and returns the result of the query.
>> This might be all the triples with the subject, or object, or both, or
>> something more complex that takes into account b-nodes.
>> So it might be nice if somewhere, such as the sitemap.xml, this query was
>> documented.
>> I think this is exactly what the "slicing" is trying to do, but instead of
>> publishing the actual query, it names the common (obvious) ones to use.
>> So a "slicing" of "subject" would tell you that you could do the query you
>> say below on the appropriate SPARQL endpoint and get exactly the same thing
>> you would get by resolving the URI.
>> So I still think that answers your question, but I'm sure you can tell me
>> if it doesn't :-)
>>
>>
>
> Ok, I see your point. However, I don't see *which* of the various slicings
> described is the one returned (ie, the equivalent query) when I resolve a
> URI... or do you mean it is always the "subject" slicing? Where is this
> stated that this slicing is what you get when resolving the URI?
>
> Cheers
> D
>
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Received on Thursday, 21 May 2009 07:58:48 GMT

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