- From: Paul Prescod <paul@prescod.net>
- Date: Fri, 02 Aug 2002 11:26:57 -0700
- To: Bill de hÓra <dehora@eircom.net>, www-tag@w3.org
Bill de hÓra wrote: > > ... or > insisting that everyone is really talking about the same thing when they > use a URI, no matter what they were saying, which is what I understand > Jonathan Borden was saying in another post (personally I find that very > bizarre, but since very little Jonathan says is bizarre, it I probably > just didn’t get it). Jonathan's point makes sense to me. Let's say the library of congress had a mechanism for accepting critiques of books. One day you come across an entry that says: "The book (not album) with ISBN XYZ is terrible." and "The album (not book) with ISBN XYZ is wonderful." Those assertions disagree both on the class of the thing and the quality of it. You can either presume that they have accidentally referred to two different things by the same name or you an presume that they are referring to the same thing and making contradictory assertions about its class and quality. I know how to handle conflicting assertions and useful semantic Web software will also. I could just presume that one of the guys looked at the object and misunderstood what it is (an album or a book) and look around for other evidence one way or the other. Detecting and dealing with contradictions is easy. But detecting and dealing with two people using the same identifier to mean different things is hard, because you can never differentiate it from a mere contradiction. "Michael Jackson is white." "No, Michael Jackson is black." Are we disagreeing on Michael's pigment du jour or talking about different Michaels? The standard way to decide is to use an addressing/naming system that we agree is globally unambiguous. "I'm talking about the Michael Jackson with this social security number. Who are you talking about?" If, after using a global identifier, we could *still* be talking about two different guys then the global identifier is useless and should be discarded. The *whole point* of global identifiers like URIs, phone numbers, social security numbers, ISBN numbers is to uniquely identify things: "The International Standard Book Number (ISBN) is a 10-digit number that uniquely identifies books and book-like products published internationally." If we can't depend upon that then you have no way to detect contradictions because you must constantly remain open to the possibility that they are really ambiguities. Another analogy: the credit card companies routinely deal with contradictions: "I bought that. I didn't buy that." But they define away ambiguity. By definition, two credit cards with the same number are the same credit card. If they detect two people using the "same" credit card (number) in conflicting ways they just invalidate the card: they do not split the card into two logical cards and try to deal with the ambiguity. They don't tell merchants: "this credit card number is being used ambiguously. Please figure out which of the two people you are talking to." They say: "This credit card number is generating an unreasonable number of contradictory statements. Please ignore that card from now on." -- XML, Web Services Architecture, REST Architectural Style Consulting, training, programming: http://www.constantrevolution.com Come discuss XML and REST web services at the Extreme Markup Conference
Received on Friday, 2 August 2002 14:28:07 UTC