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RE: [namespaceDocument-8] RDF and RDDL

From: Garret Wilson <garret@globalmentor.com>
Date: Tue, 9 Apr 2002 11:18:43 -0400 (EDT)
Message-ID: <12840.192.91.75.30.1018365523.squirrel@globalmentor.com>
To: <tbray@textuality.com>
Cc: <www-tag@w3.org>
> At 01:43 PM 08/04/02 +0100, Williams, Stuart wrote:
>>Which links the namespace with an RDF blank node that represents the
>>RDDL directory entry. The directory entry carries properties for RDDL
>>purpose, prose description and related resource. The nature property is
>>attached to the RDF node that represents the related resource.
>
> The point I keep trying to make is that the properties like
> "nature", "purpsoe", and "description", are properties <emph>of
> the related resource</emph>, not of the namespace or of the RDDL
> or of the directory entry.  T

Actually, that's only true for "description". The *nature*, as RDDL defines
it, is not a nature of the namespace but of the resource that's being
associated with the namespace. (In the words of the RDDL, "Related
resources have a nature...", not the namespace.)

The XPackage RDDL example shows this clearly:

<rddl:namespace rdf:about="http://www.ibiblio.org/xml/ns/recipe">
  <dc:description>This is a description *of the namespace*.</dc:description>
  <xpackage:style
rdf:resource="http://www.ibiblio.org/xml/styles/recipe.css"/>
</rddl:namespace>

The nature is a property of recipe.css, not of the namespace:

<xpackage:resource rdf:about="http://www.ibiblio.org/xml/styles/recipe.css">
  <rddl:nature rdf:resource="http://www.isi.edu/in-
notes/iana/assignments/media-types/text/css"/>
  <xpackage:contentType>text/css</xpackage:contentType>
</xpackage:resource>

Lastly, "purpose" is not a property value of the namespace or of the
related resource. (This is subtle.) "Purpose" describes the type of
relationship, or *why* the resource is being associated with the namespace.
(In the words of the RDDL spec, "The purpose of a resource link determines
what the link will be used for.") This means that "purpose" in RDF terms is
the predicate of the RDF statement---the property itself.

Therefore, in the example above, neither the namespace nor recipe.css would
have a "purpose" property---each property (for example <xpackage:style>
*is* the purpose of the relationship.

To give one more RDDL example for purpose: suppose a namespace is related
to mydtd.dtd with a purpose of "validation". In this
case, "rddl:validation" is actually the predicate of the RDF statement
{mynamespace, rddl:validation, mydtd.dtd}:

<rddl:namespace rdf:about="http://www.ibiblio.org/xml/ns/recipe">
  <rddl:validation rdf:resource="mydtd-uri"/>

In summary:

description: a property of the namespace
nature: a property of the related resource
purpose: the property itself that creates the association

Garret
Received on Tuesday, 9 April 2002 14:39:54 GMT

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