[topicmapmail] Meaning of URIs - ongoing debate on new W3C forum

[Thomas B. Passin]

Lars Marius Garshol wrote:

> * Thomas B. Passin
> | 
> | But as I have just posted, you still have to know how the uri is
> | being used in an rdf data set.  What you say above is so in the case
> | that a uri is used as the value of rdf:about or rdf:ID, but there
> | are plenty of other places that a uri could appear and it would not
> | "mean" the same thing.  Thus rdf has its "addressing contexts" as
> | well.
> 
> Could you give an example of where the URI would mean something else?
> The example you did give is invalid, as I explain below.
>  
> | Here's an example (omitting namespace declarations) -
> | 
> | <ex:organization rdf:about='uri:orgCentral:orgs#w3c'>
> |     <ex:homepage>http://www.w3.org/index.html</ex:homepage>
> | </ex:organization>
> 
> This is cheating, because you are giving the URI as a literal. 

That is part of my point - there are other ways to use uris in RDF - I 
meant mainly when they are the values of properties, and a literal is 
one kind of property value.  It is only in their use in rdf:about or 
rdf:ID that a uri is used as an abstract identifier.

> RDF is
> not going to recognize this as a URI at all; it's just a random
> string, no different from "5" or "cheating!". The literal doesn't
> actually identify anything, it's just itself, so here you put the URI
> in something that's not actually an adressing context.
>  

<ex:organization rdf:about='uri:example:oneMoreOrganization'
    ex:resourceRef='http://www.w3.org/index.html'/>

This is another example of a uri used as a property value.  With the 
proper definition, ex:resourceRef could mean essentially the same thing 
as a topic map resourceRef.  Note that rdf now allows one to type a 
property, so the above could have been typed with the type xsd:anyURI. 
The rdf processor would have to know that it is a uri then.

Cheers,

Tom P