W3C home > Mailing lists > Public > www-archive@w3.org > December 2007

POWDER: URIs or resources (1)

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Mon, 17 Dec 2007 13:38:54 +0000
Message-ID: <47667BEE.9010506@hpl.hp.com>
To: Phil Archer <parcher@icra.org>
CC: www-archive@w3.org, "Carroll, Jeremy John" <jeremy.carroll@hp.com>, Dan Brickley <danbri@danbri.org>, "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, Ivan Herman <ivan@w3.org>, Bijan Parsia <bparsia@cs.man.ac.uk>


A different point, that I didn't articulate in the summary message, and 
which I hope reveals that the careful thought required by the 
disciplines of RDF semantics has some value ...

Consider the following example.

foo.example.com and bar.example.com are sister sites

They mirror each other in the following way:


foo.example.com/bar  corresponds to bar.example.com

and

bar.example.com/foo corresponds to foo.example.com

so that

http://bar.example.com/foo/bar/foo/index.html

returns

http://foo.example.com/index.html

which is in fact the same as

http://foo.example.com/

This means that every resource on both sites as an infinite number of 
different URIs which identify it. (We may question the wisdom of the 
example.com site design, but the designer thinks its sexy).

Now, the /foo and /bar prefixes might be a bit of a nuisance, so perhaps 
we should create a resource set that excludes them, i.e.

<wdr:ResourceSet>
   <wdr:includeSchemes>http</wdr:includeSchemes>
   <wdr:includeHosts>example.com</wdr:includeHosts>
   <wdr:excludePathStartsWith>/foo /bar</wdr:excludePathStartsWith>
</wdr:ResourceSet>


Does this resource set include http://foo.example.com/

I suggest that the only reasonable intent is that it should, but that, 
according to the current WD, it does not.

As described above, http://foo.example.com/ is an alias for
http://foo.example.com/bar/foo/, so the resource identified by 
http://foo.example.com/ also has a URI http://foo.example.com/bar/foo/ 
which is excluded, by the wdr:excludePathStartsWith


From:
http://www.w3.org/TR/2007/WD-powder-voc-20070925/#excludePathStartsWith
[[
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 excluded when interpreting a Resource Set 
definition.
]]

===

The underlying problem is that naively we think of resources and URIs as 
in one-to-one correspondence, but in fact it is one-to-many

Jeremy
Received on Monday, 17 December 2007 13:39:35 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 7 November 2012 14:18:12 GMT