- From: pat hayes <phayes@ai.uwf.edu>
- Date: Sat, 19 May 2001 22:01:40 -0500
- To: Sandro Hawke <sandro@w3.org>
- Cc: www-rdf-logic@w3.org
> > . With my implementers hat, a resource is synonymous with a > > URI. In code I'm going to call my resource object a Resource, not, > > SomethingIdentifiedByAURIWhichMayOptionallyHaveAnchorIDs. So when I > > instruct a machine to hang a property value off a resource, I intend > > that this instruction will describe the resource not the URI that > > denotes it. Thus: > > > > urn:elvis urn:says urn:thankyuhveriimuj > > > > describes nothing about the URI urn:elvis, it's intended to describe > > whatever urn:elvis denotes: in this case, my neighbours lawn mower. > > This touches on the matter of social contract Dan Brickley mentioned. > > We agree that URIs identify things and we agree to call these things > > resources. If we didn't: > > > > urn:elvis, urn:says, urn:thankyuhveriimuj > > > > is not any more useful than saying either: > > > > "elvis", "says", "thankyuhveriimuj" >... > > In RDF, a resource is something identified by a URI (that may have > > anchor ids) as per rfc2396. That's all there is to it. I find it's > > useful way to think when it comes to implementing code. That may > > seem a backways determination; if I create a URI do I create a > > resource for it to identify? This is moot, the RDF machine can't > > access a resource directly anyway, but it allows for the description > > of say, unicorns. > >What possible advantage does "urn:elvis" (or any other URI-like thing) >have over "elvis" as a logic symbol? > >1. We can prevent unintentional re-use. This is like > com.sun.SomeJavaClass or w3c_some_C_library_function. Doing this > allows us to skip a symbol translation stage in reasoning about > two different expressions. Several problems with this include the fact that often, with names, one NEEDS to have 're-use' in order to refer to something. That is largely what names are for in social use of language, if you think about it. But I have argued this to death in earlier threads. > I think there are cases, with agents communicating in a multi-path > network, where the translation problem becomes impossible to solve > without at least a mechanism for generating unique agent (or > document) identifiers. And if you need that generation mechanism > for agents, you might as well make it available for all objects. Not all names are identifiers! Most objects do not have identifiers in this sense. A name-clash of identifiers is a computational error. Re-use of names is not. >2. There are some social mechanisms in place to designate who has > authority to define the denotation of the symbol. The clearest is > probably urn:oid, which involves a whole mechanism in > international law deligating denotational authority. (I don't > know how well it works, but I've heard it tries.) Denotational authority? Wow. You and I definitely live in different universes. There are no laws about denotational authority. The only person who has "denotational authority" (impossible to type this without smiling) over the words I use is me. > I have no idea how this actually helps, beyond the functionality > in point #1. Who cares if symbols starting urn:oid:1.2.840.113556 > may only legally be "defined" by Microsoft? How do we use that > fact? > >3. Some URIs can point humans and/or machines to some definitional > text, possibly even some permanent definitional text. But is > there an advantage to > "elvis according to the formal definition at http://example.com/elvis" > (aka "http://example.com/elvis#elvis") > over > "elvis234234" [elvis with some uniqueness mechanism] > with the nearby assertion > ("elvis234234", formal_definition_website, "http://example.com/elvis") > > The later form gives us much more flexibilty to explore approaches > to "definition", whatever that means. The denotation of my name is me, not a definitional text. > >4. Some URIs already have a pretty widely known denotation. Or do > they? What exactly does "http://www.yahoo.com" denote? Is it a > document, a service, a company, something you type into your > browser, or what? Heck, it's not even a decent URI -- it's > supposed to have a "/" on the end. You can quote RFCs 2396 and > 2616 at me, but if that meaning isnt exactly matched in the minds > of some important group of people (and I would argue it is not > yet), does it really matter? Very good questions. Pat Hayes --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Saturday, 19 May 2001 23:01:36 UTC