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Re: What do the ontologists want

From: Stefan Decker <stefan@db.stanford.edu>
Date: Fri, 18 May 2001 14:18:06 -0700
Message-Id: <5.0.2.1.2.20010517222129.031b9c90@db.stanford.edu>
To: pat hayes <phayes@ai.uwf.edu>
Cc: www-rdf-logic@w3.org
Hi Pat,

>>Rather we focus on small subsets and worry how to make them interoperable.
>
>What exactly does 'interoperable' mean? Does it imply mutually 
>consistency, for example? (If not, what does it mean?) If so, then it 
>would seem to presume that the people/agents/thingies in these small 
>subsets are at least using a language to communicate with one another that 
>has a clear notion of mutual consistency. And that requires a semantics.
You are arguing in the abstract. Let's look into a more concrete example,
eg. the scenario that Tim, Jim and Ora constructed in the Scientific 
American example:
http://www.scientificamerican.com/2001/0501issue/0501berners-lee.html

"At the doctor's office, Lucy instructed her Semantic Web agent through her
handheld Web browser. The agent promptly retrieved information about
Mom's prescribed treatment from the doctor's agent, looked up several
lists of providers, and checked for the ones in-plan for Mom's insurance
within a 20-mile radius of her home and with a rating of excellent or very 
good on trusted rating services."

Lets translate the to the actual data flow on the web:
Lucys agent contacted the doctors agent.
The doctors agent is a webservice the doctor offers on the Web.
The webservices understands a certain query language and delivers the 
resulting data in
a single, simple data schema (read: Ontology).
Then Lucy's agent looked up several lists of providers, probably from a
Yellow Pages webservice, which again understands a certain, simple query 
language
and provides data in a simple data format.
Then each provider is contacted. Same game: each provider understands takes 
a simple
query language and provides data in a simple data format.
We are not talking about large, sophisticated ontologies - we are talking about
domain models for small domains and services.

The challenge is now: we have 1 Billion different simple query languages 
and data structures.
What is the common ground that we relate each data set to each other?
We are not really talking about semantics here - that is another question.
We are talking about the foundation that is necessary
to relate one 1 Billion webservices to each other and that saves one to write
converter from each of the 1 Billion webservices to each other.
The solution is to come up with a joint data model  - and guess now - yes, 
graphs.

The database community has given the answer a couple of years and
came to graphs as a data representation mechanism. The basic idea is
that every kind of data can be represented as graphs. Thus this provides
a common ground and allows integration algorithms work easily with
multiple sources. Of course this is NOT a solution to resolve semantical
differences - it is just the necessary first step to provide a common
infrastructure.
Have I made clear, that I'm not talking about semantics here?
Should I repeat it?


>>This seems also to be much more scaleable (and, actually, realistic).
>>And then there are arguments that RDF does make much sense
>
>Stefan, you keep saying things like this to me.

I have still hope that at one point you are listening ;-)


>I havn't ever heard any of the actual arguments, however. Would you care 
>to make some?
>
>>(again, look at the semistructured data area).
>
>OK, I will.  I don't know it well, though.  Pointers?

 From database research, it is well known, that semi-structured data
(a graph form) is useful for mapping between heterogeneous datasources.
(see eg.

Papakonstantinou, Y.; Garcia-Molina, H.; Widom, J.
Object Exchange Across Heterogeneous Information Sources
1994,ICDE '95
http://dbpubs.stanford.edu/pub/1994-8

The following shows are data represented in graphs can be translated.

Correspondence and Translation for Heterogeneous Data,
Serge Abiteboul, Sophie Cluet, Tova Milo, ICDT, 1997.
ftp://ftp.inria.fr/INRIA/Projects/verso/VersoReport-102.ps.gz

or a newer paper:
Representing and Transforming Model-Based Information
by Shawn Bowers, Lois Delcambre
ECDL 2000 Workshop on the Semantic Web
21 September 2000, Lisbon Portugal
http://www.ics.forth.gr/proj/isst/SemWeb/program.html

An introduction:
Dan Suciu
An Overview of Semistructured Data
Published in SIGACT News , vol. 29 , no. 4 , pp. 28-38 , December , 1998
http://www.cs.washington.edu/homes/suciu/files/_F1446875708.ps


This following paper shows that there is much more to do in this space.
There is a lot of fine structure here, that needs to get exploited, which
really helps to resolve semantic differences in a cost effective way.
Also this paper hardly scratches the surface.
A Layered Approach to Information Modeling and Interoperability on the Web
by Sergey Melnik, Stefan Decker
ECDL 2000 Workshop on the Semantic Web
21 September 2000, Lisbon Portugal


I hope it helps,

Stefan



>Pat
>
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Received on Friday, 18 May 2001 17:17:39 UTC

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