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RE: Re[1] DAML-ONT: the case for closedness

From: Hart, Lewis <lhart@grci.com>
Date: Fri, 20 Oct 2000 14:05:00 -0400
Message-ID: <09A65DF294F8D311AAB000105A02DBAF0163E7C7@thumper.va.grci.com>
To: Pierre-Antoine CHAMPIN <pachampi@caramail.com>, Jeff Heflin <heflin@cs.umd.edu>
Cc: www-rdf-logic@w3.org, "Emery, Pat" <pemery@grci.com>
Pierre-Antoine said:
  >
  >In this case, I agree there is no problem,
  >but I believe that was not the original assumption,
  >which was that the "bad:" ontology state :
  >
  > daml:Thing isa ec:Computer
  >
  >This is were problems begin...
  >Or do you consider that the "bad:" ontology can *not* state 
  >that ? In which case, your ontologies are closed, indeed. 
  >And yes there is no problem, but it contradicts the "say 
  >anything about anything" paradigm.
  >
and also..
Jeff Heflin said:

  >Here's what it looks like in RDF (assuming http:/www.daml.org/damlont
  >and http:/www.commerce.org/econt are the daml and ec namespaces from
  >above):
  >
  >  <rdf:Description about="http://www.daml.org/damlont#Thing">
  >     <rdfs:subClassOf resource="http://www.commerce.org/econt#Computer"
/>
  >  </rdf:Description>
  >
  >This is an unfortunate consequence of RDF's "anyone can say anything
  >about anything" property." Thus, trust becomes 100 times more important
  >for ontologies than it does for ordinary RDF documents. If you
  >mistakenly trust a plain RDF document, at worst you may believe a
  >hundred false assertions. If you mistakenly trust an ontology, all of
  >your subsequent beliefs could turn out to be wrong!
  >
  >Jeff


The "bad:" ontology can state whatever it likes. The question is
do you believe it. 

If another ontology imports "bad:" then it explicitly believes it, 
to its benefit or detriment. So there will be a subset of the web, 
specifically the importers of "bad:" and their descendants, that 
believe daml:Thing isa ec:Computer. Implicitly, the disjoint subset,
those who do not import it, do NOT believe daml:Thing isa ec:Computer.

A search engine, for example, must keep track of what is
believed where/by whom. Keeping track of this could be tedious. 
If a search engine imports every ontology it comes across, the search
engine's own, internal ontology will eventually be quite a mess. Rather,
the engine needs to build articulations among it's internal ontology and
the external ones on the web. Essentially, meta facts about what is believed
by external systems, with reference to its own beliefs. This will allow
a representation of a set of sites that believe daml:Thing isa ec:Computer
without the search engine believing it internally. 

The good things about this are:

1) Anybody can still say anything.
2) There is no central authority.
  2a) Authorities will arise out of usage.
3) The scope of bad a ontology is limited.
  3a) Search engines can cut them off at the root if desired.
4) Information can still be found.

The Bad things are:

1) Systems will have to delineate between what it knows about
   and what it believes.
2) Keeping track of this could be resource intense.
3) Some sites will think everything is a computer.

- Lewis, after much discussion with Pat Emery.
___________________________________________
Lewis L Hart 
GRC International                      lhart@grci.com
1900 Gallows Rd.                  Voice (703)506-5938
Vienna, Va 22182                    Fax (703)556-4261
Received on Friday, 20 October 2000 14:05:20 GMT

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