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what RDF is not (was Re: RDF/XML Syntax Specification (Revised) W3C Working Draft published)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 20 Dec 2001 14:39:41 -0500
To: bwm@hplb.hpl.hp.com
Cc: mmoran@netphysic.com, dave.beckett@bristol.ac.uk, www-rdf-interest@w3.org
Message-Id: <20011220143941L.pfps@research.bell-labs.com>
From: Brian McBride <bwm@hplb.hpl.hp.com>
Subject: Re: RDF/XML Syntax Specification (Revised) W3C Working Draft     published
Date: Thu, 20 Dec 2001 18:30:29 +0000

How is your solution any different from the solution to a related problem below?

As far RDF is concerned both solutions depend on magic.



RDF does not have arbitrary first-order formulae?  How can I incorporate
the property consequences of first-order formulae into RDF?


Lets define a property, say bwm:also which is defined to mean that any 
property that is true of its object is also a property of its subject.
Let's also encode first-order formulae using RDF sequences.
So we could do the following:

   <rdf:Description rdf:ID="commonProps">
     <eg:form>example formula</eg:form>
     ... more shared formulae here

   <rdf:Description rdf:about="http://example.org/tom">
     <bwm:also rdf:resource="#common"/>
     .. more properties here ...

   <rdf:Description rdf:about="http://example/jane">
     <bwm:also rdf:resource="#common"/>
     .. more properties here ...

Now an application can 'know' that to determine the properties of a 
resource, as well as listing all the direct properties, it has to determine
the consequences of the formulae on objects linked through the bwm:also
property as well.  Some implementations of RDF API's, e.g. those based on
a KIF implementation, could do this very easily by loading a rule like:

   (=> (and (triple ?s bwm:also ?x) (?p ?x ?o)) (triple ?s ?p ?o))

which is just KIF for our definition of the bwm:also property.

If this data is only going to be processed by applications you write, this
is a possible way to go.  You can write the code which will check for the
bwm:also property and process it correctly, or you can use an rdf
implementation which supports KIF inferences.  However, if you send this
data to me, I don't know about and don't implement the special processing
of the bwm:also property, then information has been lost.
Received on Thursday, 20 December 2001 14:40:48 UTC

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