- From: Frank Manola <fmanola@acm.org>
- Date: Tue, 20 Dec 2005 17:14:52 -0500
- To: Henry Story <henry.story@bblfish.net>
- CC: Joshua Allen <joshuaa@microsoft.com>, semantic-web@w3.org
I don't think this is necessarily the use of rdf:type that the OO vs. duck type distinction is really about. If all you mean to do by identifying something as being of a given type is to indicate that it is a member of a set of things having a common characteristic associated with the set (and this certainly is the semantics of rdf:type), "thiefness" in this case, that by itself doesn't stress the alternatives too much. But are you also going to describe :p as being blue by saying :p rdf:type x:blueThing. as being 6 feet tall by saying :p rdf:type x:sixFeetTallThing. and so on? Most of the time, people are bundling a whole lot more into the notion of "type" than simple set-inclusion semantics, and that's where the problems often arise. For example, most people would use :p ex:color "blue"; (or some datatyped variant) in the first example instead of using rdf:type, and what they have in mind when they make that distinction is often very significant. At the same time, a slightly different interpretation of the example does get into the OO vs. duck type distinction. Suppose the two statements in question are :p rdf:type x:thief. and the other is :p rdf:type y:honest. (because two people are making the statements, they each use their own type systems, x and y). Now the issue isn't about which authority to trust, it's about what type system to use, and I needn't use either one, or I could use both. After all, the same person might be a thief according to one person's type system (say, that used by the music industry) and honest according to another's (say, that used by the American Civil Liberties Union) without contradiction; and all the other data about that person might be exactly the same. --Frank Henry Story wrote: > Oh, you are worried about typing because it may lead you to have to > make decisions about which authority to trust. That is a problem of > database consistency not of typing. If two people say something > different about someone, such as > > :p rdf:type x:thief. > > and another says > > :p rdf:type x:honest. > > You will need to decide what you should add to your database. And there > will always be many ways you can render your database consistent. You > can either reject one or the other proposals, or reject the proposal > that a man cannot be both honest and a thief. >
Received on Tuesday, 20 December 2005 22:13:51 UTC