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Re: An intuition pump

From: Jim Hendler <hendler@cs.umd.edu>
Date: Tue, 23 Sep 2003 12:21:41 -0400
Message-Id: <p05200f0fbb961bf5a693@[10.0.1.4]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: public-sw-meaning@w3.org
At 10:20 AM -0400 9/23/03, Peter F. Patel-Schneider wrote:
>From: Jim Hendler <hendler@cs.umd.edu>
>Subject: Re: An intuition pump
>Date: Tue, 23 Sep 2003 08:48:05 -0400
>
>[...]
>
>>  Anyway, my problem is that given my simple world view, I cannot find
>>  any interesting examples where Tim's solution would make smart people
>>  like Bijan and Peter so upset, yet it clearly does, which is why I
>>  ask for examples that can help a simpleton like me understand what
>>  the pragmatic effects are
>
>[...]
>
>What makes me so upset with (a strong reading of) Tim's solution is that
>eliminates many fruitful kinds of disagreement.  To communicate, one has to
>use common vocabulary, but Tim's solution requires that the meanings of
>just about all vocabulary terms are determined, in advance, by their
>owners.

This is what confuses me - as I read it, the meaning isn't determined 
with no disagreement - just the "referent" ...

>
>To pick on a similar example to Jim's, consider the vocabulary term ``Peter
>Frederick Patel-Schneider''.  (This is actually a very useful vocabulary
>term as it is almost certainly the case that there is only one person in
>the world with that name.  Further, I had to go through an unusual, and
>probably precedent-setting, process to assert my right to have that name.
>There is thus a good case to consider this and related vocabulary terms as
>being owned by me.)  Under (this strong reading of) Tim's solution, the
>mere mention of ``Peter Frederick Patel-Schneider'', or any of its
>variants, commits an agent to my view of the term.  (See my home page for
>some of the consequences.  You will probably have to view the source of the
>document as a browser is otherwise unlikely to give you the full impact.)
>


... see - this is the thing - the term "Peter Frederick 
Patel-Schneider" is some human construct and has nothing to do with 
this argument as far as I can tell.  Your home page, 
http://.../user/pfps/, is what we are talking about -- it is a 
particular place in web space that I can find.  On your home page I 
find:


...
<foaf:Person rdf:about="#Peter_Frederick_Patel-Schneider">
   <rdf:type rdf:resource="#PerfectBeing" />
...
</foaf:Person>

referring to a class defined elsewhere on your page.

I think I should now be able to unequivocally state that THIS PAGE 
claims that the person 
http://.../user/pfps#Peter_Frederick_Patel_Schneider is an object in 
the class http://.../user/pfps#PerfectBeing

Now, let's assume for the sake of the argument that I wished to 
dispute your divinity for some reason.  I have an infinite number of 
places on the web where I can state something pointing to this - for 
example, my page could say

http://.../user/pfps#PerfectBeing owl:sameAs http://.../user/hendler#Moose

where I define Moose in whatever way I wish.  Therefore...



>Under (this strong reading of) Tim's solution there is no possibility of
>divergence of opinion concerning anything about a vocabulary term.  Any
>agent who dares to disagree will just be inconsitent.

... it seems to me we have a healthy disagreement expressed neatly in 
web space without violating Tim's solution (as I understand it) 
because the things where we are referring to the same thing are 
pointing to the "boxes" but when we disagree on content we're doing 
it in different places - so an agent should be able to conclude that 
.../hendler and .../pfps disagree on something relating to 
.../pfps#Peter_Frederick_Patel_Schneider
and I can tell from the various URI and dereferencing rules what that 
disagreement is if I feel compelled to do so (note - many 
applications may simply choose to ignore the disagreement and just go 
on)

>
>I am not against the deliberate self-imposition of a fixed common meaning
>for vocabulary terms.  Even though this is not common in human discourse,
>there are many cases where a fixed common meaning is useful, in particular
>when systems with very limited reasoning power are employed.  However, I am
>against the simple use of a vocabulary term committing one to a fixed
>common meaning, and much in favour of an explicit mechanism (e.g., imports)
>for this commitment.
>

this is what I cannot really understand -- it's where I'm really 
looking for a use case that shows a difference --If you and I both 
refer (in different places) to http://.../user/pfps#PerfectBeing we 
don't need to import the page to see if we are referring to the same 
thing.  On the other hand, if we then want to find all things that 
are members of that class or what the implications of what we think 
we are agreeing on, we certainly would need to do some other work, 
which may well include importing

to put it another way - I love the fact that on the web we can, 
unlike in NLP, know if we are referring to the same "box", and the 
issues of when we need to look inside and what is meant where don't 
seem to me to be drastically different on the SW than on the WWW. 
Same URI refers to same "box", owner of URI is only one who can write 
inside that box, anyone can look inside (dereference) that box to see 
what the owner intended, any other box dereferenced that points to 
that box is bound by same rules.

So, in a sense, I interpret Tim's approach as "The owner of the URI 
gets to define what HE/SHE/IT means by that URI"   anyone else is 
welcome to say things about the owner, the predicate, the URI, etc - 
but they cannot change the "meaning" of that specific URI unless they 
do it in their space - in which case it is their claim about the 
meaning, not the owner's (and their URI is where they state what they 
claim the meaning is).

Note also that a URI with nothing there (i.e. no dereferencerable 
document or a non-document URI) works in the above anyway - the owner 
makes no claim as to the meaning of the URI, but other systems 
grounding at that URI can at least agree they are refering to the 
same "box" despite it's null content

>Peter F. Patel-Schneider
>http://www-db.research.bell-labs.com/user/pfps


  -JH
p.s Please note that I'm not responding to the issue of predicate vs. 
subject/object as determining meaning - that one seems like it could 
have some sort of import, but I haven't figured it out yet.


-- 
Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  *** 240-277-3388 (Cell)
http://www.cs.umd.edu/users/hendler      *** NOTE CHANGED CELL NUMBER ***
Received on Tuesday, 23 September 2003 12:21:47 GMT

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