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

From: Kingsley Idehen <kidehen@openlinksw.com>
Date: Sun, 22 Jul 2007 22:49:05 -0400
Message-ID: <46A41721.7070408@openlinksw.com>
CC: Linking Open Data <linking-open-data@simile.mit.edu>, Mark Baker <distobj@acm.org>, semantic-web@w3.org, www-tag@w3.org

Chris Bizer wrote:
> Hi Kingsley,
>
> I think SPARQL queries and URI dereferencing according to AWWW are two 
> seperate things.
>
> When a agent dereferences http://www.w3.org/People/Berners-Lee/card#i 
> it gets Tim's foaf profile and that's it.
>
> The agent is free to look into the data afterwards and search for 
> owl:sameAs statements. It is also free to dereference all URIs that it 
> finds within these statements. It is free to do inference or URI 
> smushing over the data. And it is free to execute SPARQL queries over 
> the dereferenced data. A good agent will do all this. But according to 
> AWWW it does not have to and it can also do other things if it likes.
>
> So I think there is no single answer to your question "What is the 
> expected result for a SPARQL Query against Tim's Structured
> Data Resource URI (aka Non Informational Resource)".
Chris,

This thread is deep, so I am reposting the question to which I responded 
initially. Note, SPARQL was used to provide backdrop to my answer.:

<<
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.
>>

My answer is/was: Yes, because he is using "owl:sameAs" to enrich the 
data exposed via his Web Page <http://www.w3.org/People/Berners-Lee/> 
(an Information Resource) associated with the Entity or Structured Data 
Resource (also known as non-information resource) 
<http://www.w3.org/People/Berners-Lee/card#i> .

The following SPARQL Queries based on Tim's usage should return 
identical results (by way of smushing), since Tim is saying: you can 
refer to me by any of these Entity aliases when exploring data in my 
Data Space (the place where the Structured Data Resource 
<http://www.w3.org/People/Berners-Lee/card#i> resides).

Examples queries would take the following form (note: the Virtuoso 
reference is just in case anyone wants to test any of our live sparql 
endpoints etc..)

SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
  <http://www4.wiwiss.fu-berlin.de/bookmashup/persons/Tim+Berners-Lee> 
?s ?p .
}

SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
  <http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007> ?s ?p .
}

SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
<http://www.w3.org/People/Berners-Lee/card#i> ?s ?p .
}

The query as executed using Virtuoso's SPARQL processor with owl:sameAs 
inferencing enabled:

define input:same-as "yes"
SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
  <http://www4.wiwiss.fu-berlin.de/bookmashup/persons/Tim+Berners-Lee> 
?s ?p .
}


define input:same-as "yes"
SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
  <http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007> ?s ?p .
}


define input:same-as "yes"
SELECT DISTINCT ?s ?p
FROM <http://www.w3.org/People/Berners-Lee/card#i>
WHERE {
 <http://www.w3.org/People/Berners-Lee/card#i> ?s ?p .
}



Anyway, I think the answer to Q3 is generally "Yes" :-)


Kingsley

>
> Cheers
>
> Chris
>
> -- 
> Chris Bizer
> Freie Universitšt Berlin
> +49 30 838 54057
> chris@bizer.de
> www.bizer.de
> ----- Original Message ----- From: "Kingsley Idehen" 
> <kidehen@openlinksw.com>
> To: "Linking Open Data" <linking-open-data@simile.mit.edu>
> Cc: "Mark Baker" <distobj@acm.org>; <semantic-web@w3.org>; 
> <www-tag@w3.org>
> Sent: Sunday, July 22, 2007 5:37 PM
> Subject: Re: [Linking-open-data] Terminology Question concerning Web 
> Architecture and Linked Data
>
>
>>
>> Chris Bizer wrote:
>>> Hi Mark,
>>>
>>> interesting point of view.
>>>
>>>
>>>> [...]
>>>>
>>>>
>>>>> 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?
>>>>> 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?
>>>>>
>>>> IMO, those URIs identify different resources.  I say this because they
>>>> all return different representations when I dereference them.  If they
>>>> identified the same resource then their representations would be
>>>> identical (see Roy's definition of resource in his REST dissertation).
>>>>
>>>> The tricky bit here is to remember to account for agency; to recognize
>>>> that although dbpedia.org uses URI #1 to identify Tim, from a third
>>>> party's POV it identifies dbpedia.org's *view* of Tim.
>>>>
>>>
>>> But I think I prefer to follow Dan's view on this 
>>> (http://lists.w3.org/Archives/Public/semantic-web/2007Jul/0102.html), 
>>> as by seeing them as URI aliases you get a nice straight architecute 
>>> that harmonizes with 303 redirects, content negotiation and alike.
>>>
>>> As you said, if they were different resources you run into problems 
>>> with agency. Seeing them as URI aliases solves these problems as we 
>>> tried to explain in our Linked Data tutorial 
>>> (http://sites.wiwiss.fu-berlin.de/suhl/bizer/pub/LinkedDataTutorial/#aliases). 
>>> Quote:
>>>
>>> "Within an open environment like the Web it often happens that 
>>> multiple information providers talk about the same non-information 
>>> resource, for instance a geographic location or a famous person. As 
>>> they do not know about each other, they introduce different URIs for 
>>> identifying the same real-world object. For instance: DBpedia a data 
>>> source providing information that has been extracted from Wikipedia 
>>> uses the URI http://dbpedia.org/resource/Berlin to identify Berlin. 
>>> Geonames is a data source providing information about millions of 
>>> geographic locations uses the URI http://sws.geonames.org/2950159 to 
>>> identify Berlin. As both URIs refer to the same non-information 
>>> resource, they are called URI aliases. URI aliases are common on the 
>>> Web of Data, as it can not realistically be expected that all 
>>> information providers agree on the same URIs to identify a 
>>> non-information resources. URI aliases provide an important social 
>>> function to the Web of Data as they are dereferenced to different 
>>> descriptions of the same non-information resource and thus allow 
>>> different views and opinions to be expressed. In order to still be 
>>> able to track that different information providers speak about the 
>>> same non-information resource, it is common practice that 
>>> information providers set owl:sameAs links to URI aliases they know 
>>> about. This practice is explained in Section 5 in more detail."
>>>
>>> Cheers
>>>
>>> Chris
>>>
>>>
>>>
>>>>> 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.
>>>>>
>>>> No.  AIUI, owl:sameAs is a very strong predicate which declares
>>>> subject and object to be the same resource.  I only foresee it being
>>>> used by a publisher to declare equivalence of their own URIs, because
>>>> being able to guarantee equivalence requires a very tight degree of
>>>> control over them (i.e. be able to serve identical representations for
>>>> all time).
>>>>
>>>> Mark.
>>>> -- 
>>>> Mark Baker.  Ottawa, Ontario, CANADA.         http://www.markbaker.ca
>>>> Coactus; Web-inspired integration strategies  http://www.coactus.com
>>>>
>>
>>
>> Chris,
>>
>> What is the expected result for a SPARQL Query against Tim's 
>> Structured Data Resource URI (aka Non Informational Resource): 
>> http://www.w3.org/People/Berners-Lee/card#i
>>
>> The generic query:
>>
>> select distinct *
>> from <http://www.w3.org/People/Berners-Lee/card#i>
>> where {<http://www.w3.org/People/Berners-Lee/card#i> ?s ?p}
>>
>> The query as executed using Virtuoso's SPARQL processor with 
>> owl:sameAs inferencing enabled:
>>
>> define input:same-as "yes"
>> SELECT DISTINCT ?s ?p
>> FROM <http://www.w3.org/People/Berners-Lee/card#i>
>> WHERE {
>>  <http://www.w3.org/People/Berners-Lee/card#i> ?s ?p .
>> }
>>
>>
>> The answer to the above is somehow getting drowned in the 
>> conversation. The answer is very important since Tim's expectations 
>> of "owl:sameAs" in this scenario are crystal clear to me.
>>
>> Note: I provided my answer at the start of this whole discussion. I 
>> am interested in yours as it is unclear to me if there is any 
>> agreement re. this matter.
>>
>>
>> Kingsley
>>
>>
>>
>>
>>>>
>>>
>>> _______________________________________________
>>> Linking-open-data mailing list
>>> Linking-open-data@simile.mit.edu
>>> http://simile.mit.edu/mailman/listinfo/linking-open-data
>>>
>>>
>>
>>
>> -- 
>>
>>
>> Regards,
>>
>> Kingsley Idehen       Weblog: http://www.openlinksw.com/blog/~kidehen
>> President & CEO OpenLink Software     Web: http://www.openlinksw.com
>>
>>
>>
>>
>>
>
>


-- 


Regards,

Kingsley Idehen	      Weblog: http://www.openlinksw.com/blog/~kidehen
President & CEO 
OpenLink Software     Web: http://www.openlinksw.com
Received on Monday, 23 July 2007 02:52:25 GMT

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