W3C home > Mailing lists > Public > www-tag@w3.org > March 2008

RE: URI Declarations [Usage scenarios 4 and 5]

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 5 Mar 2008 09:48:49 -0600
Message-Id: <p06230905c3f46c06ccef@[192.168.1.2]>
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>
Cc: "ashok.malhotra@oracle.com" <ashok.malhotra@oracle.com>, John Cowan <cowan@ccil.org>, "www-tag@w3.org" <www-tag@w3.org>
At 7:03 AM +0000 3/5/08, Booth, David (HP Software - Boston) wrote:
>  > From: Pat Hayes [mailto:phayes@ihmc.us]
>>
>>  At 12:39 AM +0000 3/3/08, Booth, David (HP Software - Boston) wrote:
>>  > [ . . . ]
>>  >SCENARIO 4: Gary publishes a lumber ontology at
>>  >http://gary.example/lumber.  The ontology includes the concept of a
>>  >standard 8-foot "2x4", which is denoted by the URI
>>  >http://gary.example/lumber#2x4x8.  Pat is writing a set of
>>  >assertions to describe the house he plans to build, and he is
>>  >interested in Gary's #2x4x8 URI, but during testing he notices that
>>  >Gary's ontology (erroneously) asserts that "30.49 inches = 1 foot".
>>  >For perhaps obvious reasons, Pat does NOT wish to accept that
>>  >assertion.
>>  >
>>  >Question: Should Pat use http://gary.example/lumber#2x4x8 to denote
>>  >a standard 8-foot "2x4" anyway?
>>  >
>>  >My answer: No.
>>
>>  OK, we disagree. I think I should contact Gary and point out to him
>>  his error,
>
>Hmm, you have a good point.  I should have used a little different
>example to differentiate between two cases:
>
>4a. The case in which the question of whether the ontology is
>wrong is somewhat subjective.  This is the case my answer should
>have been addressing, but I didn't describe the use case that way.  Sorry.
>
>4b. The case in which the ontology was correct for a long time,
>and became well used in the community, but subsequently became
>erroneous -- perhaps due to a clerical error, or maybe because
>the domain ownership was lost or hijacked.
>
>I'll try to write these up when I have time.  In the meantime, I'll 
>address your comments below as though they pertained to 4a.  I *do* 
>think the approach you describe would be appropriate for scenario 
>4b, but I think 4b should be viewed as an unusual circumstance -- 
>far less common than 4a.
>
>>  and use his URI when I do so. If I have no way to contact
>>  him, I should publish an ontology using his URI but correcting his
>>  error, and maybe (if possible) indicate explicitly that this ontology
>>  is a correction to his ontology, which is (in my opinion, of course)
>>  deprecated. Maybe I can include an annotation property to a comment
>>  indicating the reason (for humans to read). The world now has two
>>  versions of an ontology, and its up to others which they want to use.
>
>And therein lies the problem with the approach that you're 
>describing.  The world is now faced with the problem of deciding 
>which ontology to use.

THIS IS NOT A PROBLEM. This is the absolute basis of the way that the 
SWeb will succeed. I call it 'distributed syndication'. Communities 
will evolve by their mutual selection of commonly accepted 
ontologies. A key part of this is that ontologies themselves be 
connected by machine-readable links which express mutual endorsement 
(currently called 'imports', confusingly). We need, to be sure, a 
richer vocabulary of such inter-ontology connections, which was part 
of our old 'named graph' proposal, which allows ontologies to deny, 
qualify, deprecate and otherwise positively or negatively relate 
themselves to other ontologies: and indeed these ideas are creeping 
into wider use, slowly.

By the way, you say this wrong. The WORLD never needs to decide 
anything. People in the world do the deciding, and they might differ 
in their decisions. In fact, they will, whatever you or I do about 
it, and we might as well get used to that.

>  Compare this with the architectural approach that I described for 
>URI declarations: One forces the world to decide which *ontology* to 
>use -- I'll call this the ontology redefinition approach -- the 
>other forces the world to decide which *URI* to use.

Nobody forces the world to do anything. Seems to me the difference is 
that in one, but not the other, a genuine disagreement is revealed as 
a logical inconsistency between ontologies.

>  On the face of it, those options may seem quite equivalent, because 
>they both force a human to make a value judgement that is not likely 
>to be automatable.  But they're not equivalent.
>
>Under the ontology redefinition approach, given a set of assertions, 
>an application cannot determine the meaning of those assertions

?? An application can never determine meaning. SWeb applications can 
do things like detect inconsistency and subsumption, compute 
entailments, and so on.

>without *first* involving the human judgement step of searching out 
>the possible ontologies that might be defined for each URI that is 
>used, and deciding which one to invoke.

Nonsense. No application is obliged to search for alternatives. It 
will work with what it has got.

>  Under the URI declaration approach, except in case 4b (equivalent 
>to domain hijacking), an application can readily determine the 
>meaning of those assertions.  The human is only forced to search out 
>alternate URIs if he/she does not like a particular URI declaration.

The two cases seem entirely equivalent to me. In both cases, a URI is 
used in an ontology, and a human has to decide whether they like the 
ontology or not. Maybe this decision can be semi-automated, eg by 
software which reports unexpected inconsistencies and traces them to 
their source. Neither option provides any automatic way of finding a 
better ontology if all you have is a broken one: but at least if the 
URI is the same, you can embark on a search for newer ontologies 
mentioning that URI.

>
>>
>>  >  Pat should either find a different ontology to use, or mint a new
>>  >URI and indicate its relationship to Gary's URI.
>>
>>  The relationship would be owl:sameAs, so what's the point of minting
>>  a new URI? All the semantic consequence, for good or ill, follow in
>>  the same way.
>>
>>  >For example, Pat could make a copy of Gary's ontology (with Gary's
>>  >permission, of course), delete the offending assertion, change every
>>  >occurrence of "http://gary.example/lumber" to
>>  >"http://pat.example/lumber" and publish the new ontology at
>>  >http://pat.example/lumber.    The assertions for his house should
>>  >then use http://pat.example/lumber#2x4x8 instead of
>>  >http://gary.example/lumber#2x4x8.
>>
>>  WHY should I do this? What is the PURPOSE of this recommendation?
>>  What utility does it serve?
>
>It conforms to an architectural approach that allows the meaning of 
>Pat's assertions to be readily determined by other applications  -- 
>to the extent that applications can ever determine meaning, that is 
>-- without involving human intervention or judgement (except for 
>case 4b).   That's a big benefit.  It helps the Semantic Web work.

I cant see how it does anything of the sort. Right now, we can 
typically get from the URI root of a URIref to an ontology which was 
the original 'source' of that URIref, and such ontologies are 
typically treated as definitive. What is markedly different about 
your proposal?

Pat
-- 
---------------------------------------------------------------------
IHMC		(850)434 8903 or (650)494 3973   home
40 South Alcaniz St.	(850)202 4416   office
Pensacola			(850)202 4440   fax
FL 32502			(850)291 0667    cell
http://www.ihmc.us/users/phayes      phayesAT-SIGNihmc.us
http://www.flickr.com/pathayes/collections
Received on Wednesday, 5 March 2008 15:49:09 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 12:47:53 GMT