W3C home > Mailing lists > Public > public-powderwg@w3.org > April 2008

meta-DRs abd grouping by resource property

From: Stasinos Konstantopoulos <konstant@iit.demokritos.gr>
Date: Fri, 18 Apr 2008 09:13:39 +0300
To: Phil Archer <parcher@icra.org>
Cc: public-powderwg@w3.org
Message-ID: <20080418061338.GC8870@iit.demokritos.gr>

On Mon Apr  7 20:33:51 2008 Phil Archer said:

> I agree that we have to keep resource set definitions out of the picture 
> but we _do_ have a specific use case where the kind of thing you suggest 
> does occur. When we use a DR to certify another DR, it's useful to be 
> able to include a hash of the DR we're certifying. See [6]
> 
> <descriptorset>
>   <sha1sum>j6lwx3rvEPO0vKtMup4NbeVu8nk=</sha1sum>
>   <certified>true</certified>
>   <displaytext>authority.example.org certifies that claims made
>      by example.com are true. Valid throughout 2008.</displaytext>
>   <displayicon>http://authority.example.org/icon.png</displayicon>
> </descriptorset>
> 
> I just wrote this into the doc, we haven't discussed it but I'd very 
> much like to. It says that the description of the IRI set (which in the 
> full example is a single URI) has a SHA-1 hash value. There is no formal 
> semantics at work here, just a "we say that if you take a SHA-1 hash of 
> the resource, it's this value."

This looks easy enough, especially if restricted to complete POWDER docs
and not fragments (individual DRs). A POWDER doc is a resource just like
any other, so, as things stand, one can describe it with <sha1sum/> just
like any other vocabulary item. POWDER tools will have to know what to
do with this.

Generic RDF tools will have to accept the assertion that a certain
resource has a certain <sha1sum/> property. If some process provides an
alternative means for assigning this property (e.g. a tool for resolving
the resource's IRI and calculating the checksum) then the potential
inconsistency will be caught.

There is another thing one might want to express that is trickier. I
am going to use <sha1sum/> as an example, but could be any property.
I am assuming <sha1sum/> is only sensible for resolvable URL and not any
URI, so it should be at the wdrurl layer:

<dr>
  <iriset>
    <wdrurl:includeURL>http://example.com/powder.xml</wdrurl:includeURL>
    <wdrurl:includeproperty ref="sha:sha1sum">
      j6lwx3rvEPO0vKtMup4NbeVu8nk=
    </wdrurl:includeproperty>
  </iriset>

  <descriptorset>
    <certified>true</certified>
    <displaytext>authority.example.org certifies that claims made
      by example.com are true. Valid throughout 2008.
    </displaytext>
    <displayicon>http://authority.example.org/icon.png</displayicon>
  </descriptorset>
</dr>

The descriptorset applies to all documents that are at
http://example.com/powder.xml AND
have property sha:sha1sum with value j6lwx3rvEPO0vKtMup4NbeVu8nk=

This is the original resource subsumption situation, where in OWL the
assertion is made that the set of resources that have the <wdrurl:sha1sum/>
property are subsumed the the  set of resources that have the properties
in <descriptorset/>. So, on example.com all blue things are also round:

<dr>
  <iriset>
    <wdrurl:includehosts>example.com</wdrurl:includehosts>
    <wdrurl:includeproperty ref="ex:blue" />
  </iriset>

  <descriptorset>
    <ex:round />
  </descriptorset>
</dr>

s
Received on Friday, 18 April 2008 06:14:16 GMT

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