re: RDF in the ccpp.txt draft

This note is intended to summarize a discussion Graham and I have had
about the ccpp.txt draft.

It is worth noting that XML/RDF is not really intended to be written
or read by humans. It is intended as a machine readable format for
metadata. I could even imagine an CONNEG algebra to XML/RDF
compiler. Consequently, I don't think we should worry about
discovering the "ideal" encoding.

Having argued that we don't have to work towards an ideal encoding, I
do think we should convince ourselves that a reasonable encoding
exists. I have recently discovered an XML/RDF parser at:

      http://jigsaw.w3.org:8000/description

It is pretty cool. I have been using it to test some of our ideas. The
examples in this note have been tested using the w3c parser.

XML/RDF provides a rich knowledge representation framework, but it
does *not* currently support numeric data types, numeric relations or
a full complement of logical relations. One approach is to provide a
CONNEG vocabulary that defines terms for those relations.

Consider the following example CONNEG feature list:

     (&  (pix-x=640)
         (pix-y=280)
         (color=256))

A reasonable XML/RDF translation is:

<?xml version="1.0"?>

<RDF xmlns="http://w3.org/TR/1999/PR-rdf-syntax-19990105#"
  xmlns:rdf="http://w3.org/TR/1999/PR-rdf-syntax-19990105#"
  xmlns:PRF="http://www.w3C.org/TR/WD-profile-vocabulary#"
  xmlns:conneg="http://www.ietf.org/mumble/">

<Description ID="VGA display">

     <conneg:feature-description rdf:parseType="Resource">
                 <conneg:conjunction>AND</conneg:conjunction>
                 <conneg:feature rdf:parseType="Resource">
                         <PRF:pix-x>640</PRF:pix-x>
                         <conneg:relation>LE</conneg:relation>
                 </conneg:feature>
                 <conneg:feature rdf:parseType="Resource">
                         <PRF:pix-y>280</PRF:pix-y>
                         <conneg:relation>LE</conneg:relation>
                 </conneg:feature>
                 <conneg:feature rdf:parseType="Resource">
                         <PRF:color>256</PRF:color>
                         <conneg:relation>LE</conneg:relation>
                 </conneg:feature>
     </conneg:feature-description>

</Description>
</RDF>

This encoding has some nice properties:

     A. It separates the CONNEG vocabulary that defines
        relations from the feature vocabulary. This is important
     because support for multiple feature vocabularies is
     required.
     B. "feature-description" and "feature" statements nest in
        a relatively natural and human readable manner.
     C. The w3c parser finds this version acceptable.

Franklin Reynolds
Nokia Research Center