From: Frank van Harmelen (Frank.van.Harmelen@cs.vu.nl)
Date: 07/10/01
Below a proposed addition on the "syntax and semantics of URIs".
Frank.
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Syntax and semantics of URLs
Syntax:
Although there is a syntax for a general URIs, there does not appear to
be a good specification for the URIs that appear in RDF documents, in
particular, how URIs are composed in the presence of
namespaces and RDF ``fragments'', including whether namespaces are
permissable in URIs that are not XML URIs. There has been considerable RDF
debate on these points.
Semantics:
- Does the set of URL's have a non-trivial structure?
o Can two syntactically-different URIs point to the same domain element?
o can the same URI string name a different resource at different times?
o Can a URI (sometimes) fail to refer
FvH: in general, they can. In DAML+OIL, two URI's are different
unless declared to be equivalent.
- It seems reasonable to interpret URI's as logical constants. This
raises that question what the total universe of discourse is to
interpret DAML+OIL.
One possibility is to take the set AD from the denotational
semantics as consisting of exactly the URIs appearing in a given piece
of DAML+OIL. This would be the DAML+OIL equivalent of a Herbrand
interpretation. But it remains unclear what the universe of
discourse is in general.
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