owl:sameAs use/misuse/abuse Re: homonym URIs

Just to hit this owl:sameAs (ab)use nail a bit more.

Although I agree with Pat below (see my previous message) suppose I (or 
Richard) disagree(s) and want(s) to stick to the assertion
http://dbpedia.org/resource/Berlin owl:sameAs 
http://sws.geonames.org/2950159/

Does that mean that what I get from the two resources should be not only 
consistent RDF descriptions, but *identical descriptions* ? I guess so. 
It's clear that it's not the current case.
Both URI use http content negociation, and redirect (when dbpedia server 
is not 503, as it is right now :-( )  to different html pages and 
different RDF descriptions (e.g., latitude and longitude are in the 
geonames description, not in the dbpedia one) each maintained in its 
respective ___domain.

In the best of Semantic Web worlds, should not those two resources, if 
declared the same, yield indeed the *same* content trough http protocol 
(at least the same RDF content)? Which means either both URI actually 
redirect to the same one (one of them, or a third one) to ensure the 
description is unique, or the contents are somehow synchronised, which 
might be quite tricky to implement.

I would be happy to have Pat's and/or Tim's opinion on this:
Is such an implementation necessary and/or sufficient to say that 
owl:sameAs is not misused / abused?

Thx!

Bernard

Pat Hayes a �crit :
>
>> On 12 Jun 2007, at 22:07, Pat Hayes wrote:
>>>> To pick up just one point: Where do you draw the line between 
>>>> harmful punning and efficiency-increasing punning? Any rules of 
>>>> thumb for when it is OK? Why is it OK to pun with email addresses, 
>>>> but not with wives?
>>>
>>> Because people and email addresses are so different that almost 
>>> nothing you ever want to say about or do to one is ever said about 
>>> or done to the other. If you email to PatHayes, you must have meant 
>>> to PatHayes' email address. If you assert that my email address has 
>>> two children, you must have meant me. With two people (or two 
>>> mailboxes) however, things are different. There really is no way to 
>>> tell then which is meant: you can't locally disambiguate the punning.
>>
>> Here are two web pages about me:
>>
>>    <http://richard.cyganiak.de/>
>>    <http://ontoworld.org/wiki/Richard_Cyganiak>
>>
>> One is in German, the other in English:
>>
>>    <http://richard.cyganiak.de/> dc:language "de" .
>>    <http://ontoworld.org/wiki/Richard_Cyganiak> dc:language "en" .
>>
>> You say it's OK to use a web page URL to denote the person it's 
>> about, so:
>>
>>    <http://richard.cyganiak.de/> a foaf:Person .
>>    <http://ontoworld.org/wiki/Richard_Cyganiak> a foaf:Person .
>>
>> Both clearly denote the same person, so we can confidently state:
>>
>>    <http://richard.cyganiak.de/>
>>       owl:sameAs <http://ontoworld.org/wiki/Richard_Cyganiak> .
>
> Ah, no. You can't do that so, er, confidently. After all, you are 
> punning, using the same URI to denote several things, so you should 
> only say they are equal in this strong sense when they are equal in 
> ALL their uses. And of course they aren't: they denote different web 
> pages.
>
>> This allows us to conclude:
>>
>>    <http://richard.cyganiak.de/> dc:language "de" .
>>    <http://richard.cyganiak.de/> dc:language "en" .
>>
>> Which is obviously wrong. So what did I do?
>
> You overused owl:sameAs. Logical equality has to be used with care 
> when punning, its true. This is why OWL 1.1 will (at the time of 
> writing) have three distinct equalities, and why the CL semantics uses 
> true semantic overloading rather than punning, speaking strictly.
>
> BTW, I opposed including owl:sameAs, i.e. simple equality, into OWL 
> for exactly this reason. But I was overruled :-)
>
>> 1. I used the DC, FOAF, and OWL vocabulary, which are used in exactly 
>> this way all over the Semantic Web.
>> 2. I used an inference rule sanctioned by the OWL specifications, 
>> which is used all over the Semantic Web.
>> 3. I used your claim that punning is OK.
>>
>> And I arrived at an incorrect conclusion. Why, Pat?
>
> See above. But just using a sanctioned vocabulary is no safeguard 
> against getting wrong conclusions. You MISused owl:sameAs here.
>
> Equality is very dangerous. If I have two ontologies, one which treats 
> human beings as agent continuants and refers to me using 
> <http://BOF/PatHayesEnduring/>, and the other which treats humans as a 
> subclass of SpatiotemporalThings and uses a process-based ontology, 
> and refers to me as <http://FourDrUs/PatHayesTheLife/> and someone 
> casually asserts
>
> <http://BOF/PatHayesThePerson/> owl:sameAs <http://FourDrUs/PatHayes/> .
>
> because they both denote the same person, you will get the same kind 
> of error. Its not enough to just denote the same person, in some loose 
> everyday sense of 'same': it has to denote precisely the same 
> *ontological entity*. Those things can be very exactly drawn, and have 
> all kinds of metaphysical superstructure attached to them by the 
> ontologies they happen to be used in. In the case of punning, it has 
> to be thought of as a kind of n-tuple of all the things the name can 
> be used to refer to. So your owl:sameAs was just false, sorry.
>
>>> So the rule of thumb, which can be made operationally quite precise, 
>>> is that punning is OK if (there is a very high probability that) 
>>> there is enough contextual information available at the point of use 
>>> to figure out which of the various meanings is intended.
>>
>> I think on the open Semantic Web, there is a very high probability 
>> that your URI will end up in places where that contextual information 
>> is not available and thus the information consumer cannot figure out 
>> which of the various meanings was intended. It seems to me that, 
>> following your own guideline, we'd have to conclude that punning on 
>> the Semantic Web is almost never OK.
>
> Hmmm. You may be right. Certainly it would be safer, if we could 
> manage it. But I don't think we can possibly manage it.
>
> But you have made a very nice case, which nobody has made to me 
> before. Thanks.
>
> Pat

-- 

*Bernard Vatant
*Knowledge Engineering
----------------------------------------------------
*Mondeca**
*3, cit� Nollez 75018 Paris France
Web:    www.mondeca.com <http://www.mondeca.com>
----------------------------------------------------
Tel:       +33 (0) 871 488 459
Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com>
Blog:    Le�ons de Choses <http://mondeca.wordpress.com/>

Received on Thursday, 14 June 2007 10:56:38 UTC