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Re: DAML+OIL (March 2001) released

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Mon, 2 Apr 2001 11:23:18 -0400 (EDT)
Message-Id: <200104021523.LAA08828@pantheon-po02.its.yale.edu>
To: seth@robustai.net
CC: jonas@rit.se, phayes@ai.uwf.edu, www-rdf-logic@w3.org

   From: "Seth Russell" <seth@robustai.net>

      From: "pat hayes" <phayes@ai.uwf.edu>

      >RDF
      > triples have no special syntactic advantages over, say, LISP
      > Sexpressions, and they provide no special functionality or semantic
      > power.

   While I think this is doubtlessly true; since we can transform any triples
   diagram into sexpressions and visa versa without loss (can't we?); it would
   seem to me that there is an advantage in thir simplicity.  Of course, the
   enthusiasm for the triples in the community at large is also an advantage,
   imho.

There is no problem with considering triples as S-expressions.  The
problem is considering them as S-expressions *and* as a formal
descriptive language simultaneously.

Suppose someone suggests the use of Unicode as a formal language, along
the following lines.  Let the letter "l" stand for "lives in."  Let
"W" stand for George W. Bush.  Let "D" stand for Washington, D.C.
Let "T" stand for Tony Blair, and "L" for London.  Let "t" stand for
`taller than.'  And so forth.  Make sure every printing character is
assigned a meaning.  Now take any string and divide it into groups of
three characters, and assign to "pqr" the meaning "the relation
denoted by p holds between the object denoted by q and the object
denoted by r."  The whole string then stands for the conjunction of
the propositions denoted by the letter triples.  So the string
"lWDlTLtTW" means "George W. Bush lives in Washington, D.C., Tony
Blair lives in London, and Tony Blair is taller than George W. Bush."
Call this scheme URF, for "Unicode Representation Format."  

Now suppose I argue that URF isn't a very powerful language, for
reasons that I hardly need to enumerate.  It would be frustrating if
the pro-URF faction comes back with the rejoinder, "What do you mean,
it isn't very powerful?  You can represent *anything* in Unicode, can't
you?  Isn't it useful to have a `common exchange protocol'?"

This may sound like a parody, but to me statements such as this one by
Seth seem to be of exactly this type:

   Inferencing is an application that sits on top of the triples ... let the
   best one win.  I fail to see how this is an argument against simply using
   triples.

In my URF world, couldn't I say  

 Inferencing is an application that sits on top of the Unicode ... let the
 best one win.  I fail to see how this is an argument against simply using
 Unicode.

The point is that no one is arguing against using Unicode or RDF as a
coding scheme; the argument is against using either as a formal
language.  If RDF is simply an encoding scheme, then we can put it on
the back burner and focus on the language actually being encoded.  
If we view it *as a formal language*, then its flaws loom large.  It
lacks many key features, including implication and bound variables.

Actually, I am not convinced that it's such a great encoding scheme.
I am told it goes beyond XML in some important ways, but I'm not sure
what they are.

   >The RDF documentation and discussion archives are rife with
   > elementary errors (such as confusing use and mention, confusing
   > syntactic structure with meta-description, confusing asserting with
   > reference, confusing names with URIs, and confusing dereferencing
   > with denotation) that they often border on being simply incompetent.

   Hey man! ...then give us a hand ...

As I have argued before, I don't think it would be particularly
difficult to fix the problems with RDF.  However, fixing them would
require thinking of an RDF expression as a self-contained textual
object, which seems to be incompatible with thinking of it as a piece
of a graph, and therefore incompatible with the triples model.  I
think this is where we're stuck.

                                             -- Drew McDermott
Received on Monday, 2 April 2001 11:23:33 GMT

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