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operationally, ResourceSets are sets of URIs not resources

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Thu, 20 Dec 2007 15:42:46 +0000
Message-ID: <476A8D76.6040900@hpl.hp.com>
To: public-powderwg@w3.org


On my reading of the POWDER WDs, the intent with the definition of a 
ResourceSet is that, given a URI u, you can use each part of the 
definition in turn, to test whether u is in the resource set or not.
However, it is not the intent that you can use each test in the 
description of a ResourceSet independently of the other tests.

Thus, a ResourceSet operationally defines a set of URIs, and we can then 
consider the set of resources, which are identified by those URIs.

===

Now, this seems straight forward, but is less so, when we consider a 
resource which has two URIs identifying it.

Suppose R is a resource
   identified by http://example.org/r and by http://example.com/s


<wdr:ResourceSet rdf:ID="RS1">
   <wdr:includeHosts>example.org</wdr:includeHosts>
   <wdr:includePathsStartsWith>/s</wdr:includePathsStartsWith>
</wdr:ResourceSet>

The intent seems to be that R is not in this resource set.

The operational rules when processing both http://example.org/r and 
http://example.com/s do, indeed reject both.

But the descriptions of both in the vocabulary document, permit R to be 
in the resourceset

http://www.w3.org/TR/2007/WD-powder-voc-20070925/#includeHosts
[[
This property defines a set of resources, that have a URI host component 
matching at least one of the values given in a white space separated 
list, that is to be included when interpreting a Resource Set definition.
]]

So that R has a URI http://example.org/r and is included.

http://www.w3.org/TR/2007/WD-powder-voc-20070925/#includePathStartsWith
[[
This property defines a set of resources, that have a URI path component 
starting with at least one of the values given in a white space 
separated list, that is to be included when interpreting a Resource Set 
definition.
]]

So that R has a URI http://example.com/s and matches.

I suggest this can be addressed by aligning the semantics with the 
operational definition, and having a resource set being a set of URIs, 
with the mapping to resources being done elsewhere (e.g. in the 
definition of
http://www.w3.org/TR/2007/WD-powder-voc-20070925/#hasScope

i.e. change
[[
This property links a Description Resource to the set of resources to 
which it applies. It MUST be included in Description Resources.
]]

to
[[
This property links a Description Resource to the set of URIs of the 
resources to which it applies. It MUST be included in Description 
Resources. Any resource which has a URI in the set of URIs is in scope 
for the Description Resource.
]]

Jeremy
Received on Thursday, 20 December 2007 15:43:24 GMT

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