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Re: [Linking-open-data] Terminology Question concerning Web Architecture and Linked Data

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Sat, 07 Jul 2007 15:23:59 -0400
Message-ID: <468FE84F.2030405@openlinksw.com>
To: Linking Open Data <linking-open-data@simile.mit.edu>
CC: www-tag@w3.org, semantic-web@w3.org

Chris Bizer wrote:
> Hi all,
>
> Richard Cyganiak, Tom Heath and me are currently writing a tutorial on how 
> to publish Linked Data [1] on the Web and ran into some terminology 
> questions concerning Web Architecture.
>
> Here is the problem statement together with an example: Within the Linking 
> Open Data community project [2] different data sources (URI owners) publish 
> information about Tim Berners-Lee using different HTTP URIs:
>
> 1. DBpedia: http://dbpedia.org/resource/Tim_Berners-Lee
> 2. Hannover DBLP Server: 
> http://dblp.l3s.de/d2r/resource/authors/Tim_Berners-Lee
> 3. Berlin DBLP Server: 
> http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007
> 4. RDF Book Mashup: 
> http://www4.wiwiss.fu-berlin.de/bookmashup/persons/Tim+Berners-Lee
>
> The first 3 data sources follow the W3C TAG "Dereferencing HTTP URIs" 
> finding [3]  and redirect via HTTP 303 to documents describing Tim 
> Berners-Lee when the URIs are dereferenced over the Web. Therefore, the URIs 
> identify Tim Berners-Lee as a non-information resource. This redirect also 
> supports HTTP content negotiation and leads to HTML as well as RDF 
> descriptions of Tim.
>
> 5. Tim also publishes a FOAF profile in which he assigns the URI 
> http://www.w3.org/People/Berners-Lee/card#i to himself.
>
> Question 1: According to the terminology of the Architecture of the WWW 
> document [4] are all these URIs aliases for the same non-information 
> resource (our current view) or are they referring to different resources? 
>   


They are all "Associated" but not "Equivalent" physical Web Resources 
(information-resources i.e. Web Accessible files) [1] that expose data 
related to the individual (non-information resource): Tim Berners-Lee.  
They collectively or individually produce RDF Data Sets containing 
Literal Objects: "Tim Berners-Lee" in conjunction with explicit URI 
references to Tim's Personal URI: 
<http://www.w3.org/People/Berners-Lee/card#i> . I think "rdfs:seeAlso" 
[2] is a more unambiguous mechanism for expressing these associations 
across Data Sets (Data Sources).

I have saved an RDF Browser session [3] that should illustrate my 
position above.
> Does the TAG finding "On Linking Alternative Representations To Enable 
> Discovery And Publishing " [5] about generic and specific resources apply 
> here, meaning that the URIs 1,2,3,5 refer to different specific 
> non-information resources that are related to one generic non-information 
> resource?
>   
Yes. (imho).

> Question 2: When the URIs are dreferenced they provide quite different 
> information about Tim, which reflects the knowledge and the opinion of the 
> specific URI owner about him. Within our tutorial we need to talk about this 
> information and therefore need a term to refer to a concept that can be 
> described as "information provided by a specific URI owner about a 
> non-information resource", for example Tim. Depending on the answer to 
> question 1, what would be the correct Web Architecture term to refer to this 
> concept? Or is such a term missing?
>   
I think this term is missing.

I have used to term: Data Space to attempt to canonicalize what is 
basically a "Universe of Discourse" as perceived by the owner of the 
Data Space from these URIs emanate.

> Question 3: Depending on the answer to question 1, is it correct to use 
> owl:sameAs [6] to state that http://www.w3.org/People/Berners-Lee/card#i and 
> http://dbpedia.org/resource/Tim_Berners-Lee refer to the same thing as it is 
> done in Tim's profile.
>   
Depends on the characteristics of the property "owl:sameAs" as used in 
Tim's "Universe of Discourse" (Data Space) and here is why:

Yes, if in Tim's Data Space Definition he asserts that "owl:sameAs" is 
an "owl:SymmetricProperty" then his usage is unambiguous, as this should 
result in identical triples when you SPARQL against his Data Space using 
either URI (assuming we are not modeling the Web as a single Graph). Of 
course, this assumes the SPARQL processor has inference capabilities. 
Otherwise, "rdfs:seeAlso" would be the preferred property as this is 
unambiguous (i.e. the aforementioned URIs will produce varied Triples 
without introducing confusion).


Links:

1. http://www.w3.org/TR/owl-ref/#sameAs-def
2. http://www.w3.org/TR/2000/CR-rdf-schema-20000327/#s2.3.4
3. 
http://demo.openlinksw.com/DAV/home/demo/Public/Queries/DataWeb/Physical_RDF_Web_Resources_Associated_with_TimBL.wqx

> Any clarifications on these question would be highly welcomed.
>
> Cheers
>
> Chris
>
>   

-- 


Regards,

Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com
Received on Saturday, 7 July 2007 19:24:26 GMT

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