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RE: Where are the semantics in the semantic Web?

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 23 Nov 2005 18:31:11 -0500
Message-Id: <p06230938bfaaa9dac883@[172.31.0.192]>
To: "Shi, Xuan" <xshi@GEO.WVU.edu>, "'drew.mcdermott@yale.edu '" <drew.mcdermott@yale.edu>, "''public-sws-ig@w3.org ' '" <public-sws-ig@w3.org>

At 12:14 -0500 11/23/05, Shi, Xuan wrote:
>Also I think we may focus the discussion on the semantics (the meaning) of
>services and functions first rather than the meaning of vacabulary used in
>the description document, even the semantics/meaning of "city" is different
>in different parts of the world. So when we use "city" in WSDL or any other
>document, do we need to clarify that the definition of "city" means that it
>should have more than 5000 people or 25000 people, in UK or in USA or
>somewhere else. CS people may not be capable to deal with such cultural
>issues.

Shi the amazing thing is you understand the problem so well, but are 
so far from understanding the solution --  look,  you point out above 
that the exact problem is that people can't agree throughout the 
world on what a city is or just about anyone else -- consider, for 
example,
first and last names - we use them every single day of our lives, but 
we don't have a single agreement as to order across cultures and 
communities - If you have a web service that takes as arguments
  "first name, last name" then I don't know whether to send it "Shi 
Xuan" or "Xuan Shi" without more information.  Any approach that 
requires getting everyone in the world to agree (like it did for your 
hotel example) is impossible.   The alternative is to have words 
specified in context, and to have ways for people and/or machines to 
determine that context.  So if you said
http://ww.cs.umd.edu/hendler/peopleont#firstname then there could be 
a document at that URI with some text (for people) or RDFS/OWL (for 
machines) that helped explain your use of the referent.  Even if 
there isn't, if you and I agreed to use that term in a certain way, 
we wouldn't have to convince anyone else to agree with us - because 
someone using a service that took this input would never confuse it 
as being equal (as it would be in English) to some other 
http://foo.bar.baz/services/servont#firstname.   In you Xlink-like 
scheme, there is no way to distinguish different users using the same 
string, so we need to get the impossible global agreement.  When we 
use URIs at least that aspect of the problem goes away
  So despite Drew's earlier flippant answer, there really is a 
difference between syntax and semantics used in the sense of 
"grounded symbols" where the grounding is in URI space.
  One reason some of us are getting frustrated is we have written much 
about this in the past - for example, if you read the Scientific 
American article by Berners-Lee et al, or my slides from XML, or etc. 
you would find lots of discussion of this issue -- and the RDF, RDFS, 
and OWL documents speciify EXACTLY (in a deep technical sense) what 
we mean by machine readibility of these relations and what can (and 
cannot) be iassumed when terms are the same or are defined in Sem Web 
documents.
  As for me, this is my last attempt - I've written too many such 
responses to many people about this, and if you want to try to get a 
service language that works by natural language agreement, instead of 
something more formal, all power to you -- I think it is a doomed 
enterprise, but I could be wrong
  -JH


>
>-----Original Message-----
>From: Jim Hendler
>To: drew.mcdermott@yale.edu; 'public-sws-ig@w3.org '
>Sent: 11/22/05 6:08 PM
>Subject: RE: Where are the semantics in the semantic Web?
>
>Xuan Shi -
>    Let me once again point you to the slides from my XML talk [1] - I
>contrasted Xlink (which is essentially identical to what you propose
>to do for services) to RDF, showing why they are crucially different.
>There's a big difference between what you have below (because I am
>unsure what "roomtype" is and what values are allowed) and
>http://ex.org/hotel#roomtype which could dereference to an RDFS or
>OWL document which would exactly answer that question.  I could also
>then tell if Holiday Inn's "roomtype" and one at some Inn in Japan or
>China was the same thing, or something that might be different --
>these are not minor differences - the focus on links is crucial to
>understanding the Semantic Web as I said in that talk
>   -Jim Hendler
>
>[1] http://www.cs.umd.edu/~hendler/presentations

-- 
Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	  	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742	 		  http://www.cs.umd.edu/~hendler
(New course: http://www.cs.umd.edu/~hendler/CMSC498w/)
Received on Wednesday, 23 November 2005 23:31:53 GMT

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