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Re: [URI vs. URIViews] draft-frags-borden-00.txt

From: Jonathan Borden <jonathan@openhealth.org>
Date: Fri, 22 Feb 2002 22:40:45 -0500
Message-ID: <03c101c1bc1b$e3e72600$0301a8c0@ne.mediaone.net>
To: "Pat Hayes" <phayes@ai.uwf.edu>
Cc: <www-rdf-comments@w3.org>
Pat Hayes wrote:

> >
> >What is a "subresource" of Unicorn:
> >
> >suppose the URI http://example.org/Unicorn which identifies the resource
> >Unicorn
> >the URI reference http://example.org/Unicorn#LeftButtock identifies the
> >"subresource"
>
> ****
> OK, but that isn't the way RDF uses frags. A fragId doesn't indicate
> a mereological part, like a buttock or a kidney; it identifies a
> piece of text in an RDF *document*.

Careful, RDF uses frags in two ways:

1) as you say
2) any subject,predicate or object of any statement may be identified by a
URI reference. Such URI references may have a fragment id.

e.g.

<http://example.org/Unicorn#Bottock> rdf:type foo:Bar
<http://example.org/Unicorn> rdf:type foo:Unicorn

does not imply any relationship between foo:Bar and foo:Unicorn

The URI reference that identifies the subject of the first statement has a
fragment identifier.

> If http://example.org/Unicorn
> really means a unicorn, then it should never have a fragId attached
> to it in RDF.

Really! This is exactly Aaron's argument. A unicorn is an example of what
some people call an "abstract resource".

The way RDF would interpret
> http://example.org/Unicorn#LeftButtock  would be that the absolute
> URI is the URL of a Web document containing some RDF text that uses
> the identifier 'LeftButtock', and presumably contains some RDF
> assertions about the entity that it identifies.

No this is the whole point. If one RDF treats URI references as opaque
identifiers, then one can make any statement about any URI reference. This
is the whole argument. Should RDF treat URI references as opaque or not?
Should all URIs that use the "http" scheme identify _documents_ or might not
the URI http://example.org/Unicorn identify a Unicorn..

For example,does your model theory contain anything pertaining to the
syntactic substructure of a URI reference? scheme, authority, heirarchical
part, fragment id? I don't see it.

 But the referring
> thing here is the whole uriref, not the absolute URI. That doesn't
> refer to anything but the document. The relationship between
> http://example.org/Unicorn and http://example.org/Unicorn#LeftButtock
> is not one of resource to subresource;

Read the internet draft carefully. There is no _relationship_ defined
between _resource_ and _subresource_. A document does contain fragments. One
might consider a sub resource to be contained by  a resource but one can
make entirely independent assertions about a resource and any of the
subresources that it supposedly contains. A resource 'contains' a
subresource when the resource is a namespace but not generally (unless you
are also willing to say that the "http" scheme contains the set of "http"
based URIs.

>
> For example, look in  http://www.w3.org/1999/02/22-rdf-syntax-ns. It
> contains XML-encoded RDF assertions which use, for example,  the term
> called there by the string 'Class'.

By "look in" you mean HTTP GET I presume. What is returned is not a resource
but, _by definition_, a network entity. It is the _entity_ which contains
XML encoded RDF assertions.

So yes the _document fragment_ obtained by _resolving_
http://www.w3.org/1999/02/22-rdf-syntax-ns#Class is a piece of XML. And the
_document fragment_ is indeed contained in the document (entity).

It is very common to conflate a resource and the entity that represents it
at any point in time. But whether you agree or not, this is how the language
is defined. It is not possible to understand anything about "REST" until
this distinction is undetstood at least from a terminological point of view.

Jonathan
Received on Friday, 22 February 2002 22:31:52 GMT

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