- From: Frank Manola <fmanola@mitre.org>
- Date: Tue, 19 Jun 2001 09:04:28 -0400
- To: Brian McBride <bwm@hplb.hpl.hp.com>
- CC: w3c-rdfcore-wg@w3.org
Brian McBride wrote: > > Frank Manola wrote: > [...] > > I agree. It's just that I think the concepts of type (or Class), and > > specific classes like Statements, are in the base layer already. > > Does n-triple have a notion of type or class? [Is there an actual definition of n-triple you can point me to? If so, maybe I could be more definitive about these answers; but maybe not!] I guess the answer is in two parts. First, I assume we have to define "n-triple" itself (that is, the thing that corresponds to a "statement"), along with its components "resource", "predicate", and so on. Aren't those built-in types or classes? If they are, then it seems to me we ought to account for those ideas in the base layer (more clearly than is currently done in the M&S formal model by merely saying they are "sets"). In other words, I think that the base layer (and the current formal model) ought to be reasonably closed, without appealing to other specifications to complete the definition of its basic ideas. The second part is, aren't we (at least implicitly) assuming that RDF is used to develop typed data models? This is certainly true of all the examples I've seen. If that is true, then once again it seems to me we need to say that in the base layer. I imagine we could define the notion of types in the base layer without necessarily assuming that every schema language would also define subtypes and inheritance. We could also assume there are types in the base layer without necessarily assuming a schema language that allowed user-defined types (certainly lots of older programming languages did that). Mind you, I'm not necessarily advocating these latter things. But if we're going to define a principled set of layers, we ought to be clear about the amount and types of variability we intend to allow in the upper layers, based on the lower layers. If, for example, we assume RDF is essentially a typed data model, it seems to me that moving basic types to the base layer has no potential adverse effects, and helps clarify the definition of the base layer concepts. (I think that even if someone is thinking of using RDF in an "untyped" fashion, all that really means is that they won't be specifying user-defined types; we would still expect them to use "resource" and "predicate" wouldn't we?) --Frank -- Frank Manola The MITRE Corporation 202 Burlington Road, MS A345 Bedford, MA 01730-1420 mailto:fmanola@mitre.org voice: 781-271-8147 FAX: 781-271-8752
Received on Tuesday, 19 June 2001 09:09:40 UTC