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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Semantic Web permathread, iteration n+1 (was Re:
 Thomas B. Passin wrote: > Elliotte Rusty Harold wrote: > >> At 9:56 PM -0400 6/4/04, Thomas B. Passin wrote: >> >>> Right, an arbitrary piece of xml does not carry enough information to >>> let you automatically distinguish between elements that represent >>> things and those that represent properties. A person generally has >>> to work that out. But when you do have a properly striped format, it >>> can be easy to turn into rdf (it's usually just about there as is). >> >> >> >> >> Why is there a distinction between "things" and "properties"? Isn't a >> property a thing? Can't a property have properties of its own? > > > In RDF, a Property is a kind of Resource, and you can in fact make > statements about it. However, apparently, this kind of practice > prevents many kinds of logical reasoners (or maybe all, I am not expert > enough to know) from being "sound" and /or "complete", so most of the > restricted logics (like various forms of Description Logics) restrict > the kinds of constraints you can place on properties (which is in effect > restricting what you can say about them). The goal of such restrictions > is to make sure that a reasoner can complete any assignment in a > reasonable time (such a polynomial time as opposed to, say, exponential) > and be sure that any answer is correct. Doesn't this represent a flaw somewhere in RDF? Why are the examples in RDF of things that do not correspond to hierarchies (unless striping (or perhaps more semantically, 'grouping') is used)? Simplistic examples of things that will never have a hierarchy do not help. ? -Rob 
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