- From: pat hayes <phayes@ai.uwf.edu>
- Date: Thu, 12 Jul 2001 13:07:13 -0700
- To: <bdehora@interx.com>
- Cc: w3c-rdfcore-wg@w3.org
>:Brian McBride: >: >:On the question of literals as resources, I've looked through >:the recent >:email traffic and the logs and minutes of last Friday's >:discussion. I'd >:like to test support for this position: >: >: o the WG agrees that URI's can be assigned to denote literals. > >Is this to say: the wg indicates that people may assign URIs >to Literals in their RDF data? I think I would be fine with >this, but I still don't understand what is being described. >Is a Literal simply a resource that can be present in the >web (ie on a computer)? Seems to me that there are at least three possible positions one could adopt here. 1. URI's may be assigned to literals, in the sense that the language (in some future version) allows one to assert that something denoted by a literal is also the referent of a URI, so that an equality of the form (= <URI> <literal> ) could be asserted (maybe not with this syntax, but you get the idea.) 2. At the other extreme, the language could be understood relative to a semantics in which the things denoted by URI's and the things denoted by literals were required to come from disjoint (subsets of the) universe(s), so that it would be logically impossible for such an identity to every be true. ON this view, providing literals for some range of values effectively removes those things from the normal domain of quantification, so that it is impossible to have the same relation between, say, thingies and integers as it is between thingies and thingies. 3. An agnostic version where there was nothing which *required* that a URI could not denote a literal value, but on the other hand the langauge does not *provide* any way to express a URI-to-literal link, so that there are no URI-to-literal assignments and no ways to express identities of the above kind between URI-denoted things and literal-denoted things (such as strings or integers). I would urge the advantages, in a language that purports to be very general-pupose, of agnosticism of the third kind. That leaves the door open for a future extension or modification of the langauge of the first kind. DAML+OIL took the second route, drawing a sharp semantic contrast between objects and literal values, for essentially computational reasons: to let the two domains 'mix' would have produced language constructs that would have had unknown inferential complexity (or known intractability), and there was seen to be an overarching requirement to keep DAML reasoning tractable, or at least decideable. But other languages might take other directions. Pat Hayes --------------------------------------------------------------------- (650)859 6569 w (650)494 3973 h (until September) phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Thursday, 12 July 2001 16:07:17 UTC