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Re: Syntax vs Semantics vs XML Schema vs RDF Schema vs QNames vs URIs (was RE: Using urn:publicid: for namespaces)

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 14 Aug 2001 12:21:25 -0700
Message-Id: <v04210111b79f271cf405@[]>
To: Patrick.Stickler@nokia.com
Cc: www-rdf-logic@w3.org
>Well, I'm probably going to get grilled for this comment, but personally
>I don't like anonymous nodes. After all, just what *is* an anonymous
>node. Every application that I've seen that uses them has had to give
>them some form of identity, and yet that identity is system dependent.

The NODE has an identity, but it doesnt have a label which denotes 
anything. The easiest way to understand anonymous nodes is just like 
existentially quantified variables in logic, ie they assert that 
something exists (just like a name or a URI does) but they don't give 
it a name (unlike a name or a URI). That is widely considered to be a 
handy thing to be able to do, and it is well-defined and seems 
harmless, so why not allow it?

>IMO, anonymous nodes were a hack to allow collection structures as Objects,
>but yet collections (or rather ordered collections) in RDF do not work in
>an context of multi-source syndication (nor do DAML collections either).
>The proper way IMO to model collections is using an ontology of collection
>relations and plain old triples with no anonymous nodes; but that's a
>discussion that I don't want to start here.

Nothing would be greatly changed if all anonymous nodes were made 
non-anonymous, but there would be a lot of silly names cluttering up 
things to no useful purpose.

>Issues of completeness required by the closed world folks can be addressed
>by assigning source or authority to statements so that one can selectively
>filter those collection members defined in a particular source or by
>a particular authority and "outsiders" cannot add to that "view" of the
>collection. IMO, the RDF conceptual model should have no anonymous nodes.
>Collections based on serialized, syntactic structures should have no
>realization in the underlying conceptual model; but again, that's yet
>another discussion ;-)

That is certainly another point of view about collections, but there 
are other reasons for allowing anonymous nodes.

>I will concede that there *might* be valid and necessary uses for anonymous
>nodes which I am not yet aware of, but irregardless I get the impression
>(and I may very well be wrong, apologies in advance) that anonymous
>nodes are the new, "hot", interesting thing in RDF/DAML and so folks are
>predisposed to using them to solve every problem even when more
>constrained, simplier, and better alternatives may be available.
>For those who are convinced that anonymous nodes are a good thing, please
>think about the implementational burden and portability/interoperability
>issues they may introduce.

What burdens and issues? .

Pat Hayes

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(650)494 3973 h (until September)
Received on Tuesday, 14 August 2001 15:20:51 UTC

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