W3C home > Mailing lists > Public > www-rdf-logic@w3.org > July 2003

Re: Semantic Web issues

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Sat, 19 Jul 2003 11:23:58 -0400 (EDT)
Message-Id: <200307191523.h6JFNwA13022@pantheon-po04.its.yale.edu>
To: abcharl@keyworld.net
CC: www-rdf-logic@w3.org

   Date: Fri, 18 Jul 2003 07:26:17 +0200
   X-PH: V4.4@mr1
   From: "Charlie Abela" <abcharl@keyworld.net>

   His view of the Semantic Web (of which Web Services is a specific sub-part)
   is that it is primarily (if not practically exclusively) focused on
   expressing the meaning of information as the author intended. Except that he
   believes that it is extremely limiting. He argues that discoveries are made
   by taking data and interpreting it in an unexpected 'context'  (whatever
   context means) and that the approach that is being considered by the
   Semantic Web community to information representation and reasoning may
   prevent information discovery.

It would be nice to have an example of what he means by information
discovery.  If I discover where the nearest kosher pizza place is,
does that count?

   Reasoning in the Semantic Web is monotonic and makes an open world
   assumption, rather than nonmonotonic and making a closed world assumption.

Why is SW reasoning monotonic and open-worldish?  Who will enforce
these constraints?

   He is reluctant to believe that taking an open world, monotonic approach to
   reasoning will necessarily ensure that the information transmitter/receiver
   will actually be able to work out that they are "talking" about the same
   thing without first decontextualising the data being reasoned with/about,
   which he argues that in itself this is intractable.

He's right that figuring out that two different info sources on the SW
are talking about the same thing is very difficult.  I don't see what
being open-worldish or monotonic has to do with the problem.  And I
don't know what "decontextualising" means.

   He is also concerned about the approach taken by the Semantic Web that
   assumes that information (data in context) is consistent, ....

Surely no one assumes that all the information on the SW is

   ... because
   i) this is only possible with undisputed/indisputable facts (which are only
   a proportion of the 'information' humans use to reason with/about), and
   ii) will it necessitate a Microsoft-like company to make available (for a
   fee, of course!) consistent information for open world, monotonic  reasoners
   to use?

I would think that if someone can supply a large body of useful
information to the world they should be able to charge for it,
although they may have a hard time collecting given the ability of
buyers to share among themselves.

I think people tend to overreact to the possibility of inconsistency.
They're visualizing smoke coming out of their laptops, as it does on
Star Trek.  In fact, an inference system might make good use of a data
collection without noticing that it has an inconsistency.  If it does
notice, it's faced with the task of figuring out which information
sources are either in conflict with each other or internally
inconsistent.  There are a variety of simple tactics it can try, such
as trying to solve problems without using tainted information
sources.  It can also complain to the vendors.  It can go looking for
better sources.  Etc.

For example: Suppose an agent is trying to find the best price for a
lot of 1000 bolt-nutters it is tasked to buy.  It uploads the 
information from each bolt-nutter vendor about how to query and order,
and uses it to find the vendor with the lowest price.  If it discovers
that a vendor's information is inconsistent, it should notify the
vendor and drop it from the list.  The vendor will be strongly
motivated to clean up its data.

A feature of this scenario that people tend to overlook is that the
places the agent looks for information are limited to a few sites that
are strongly suggested by the task at hand.  Scanning the whole web on
the off chance that someone in Budapest has a convincing argument that
bolt-nutters are obsolete is simply not going to happen.

                                             -- Drew McDermott
Received on Saturday, 19 July 2003 11:24:02 UTC

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