W3C home > Mailing lists > Public > www-rdf-interest@w3.org > April 2000

Re: Some questions on properties

From: Jan Wielemaker <jan@swi.psy.uva.nl>
Date: Wed, 26 Apr 2000 20:50:57 +0200
Message-Id: <200004261850.UAA23340@gollem.swi.psy.uva.nl>
To: Jan Wielemaker <jan@swi.psy.uva.nl>, www-rdf-interest@w3.org, stefan@db.stanford.edu
> At 09:30 AM 4/26/00 +0200, you wrote:
> >Thanks Stefan
> >
> >[ As you probably guess, I decided to have a look at interpreting
> >   RDF directly in Prolog.  Sofar it looks rather trivial.  Less then
> >   300 lines of Prolog provide me with a Prolog structure ready for
> >   generating triples (on top of the output of an XML parser).  I
> >   now try to understand the semantics :-
> 
> Great! But interpreting RDF isn't the easiest part.
> I assume many people are interested in the code.
> 
> 
> >   P.s. I failed to find a good test-suite.  Does it exist?
> >]
> Unfortunately, not yet....

Thats really a pity.  Dispite, I'm making very good progress.  I'm
testing what I think is a complete RDF compiler in Prolog.  The whole
thing is now 550 lines.  It will get a little bigger if I comment the
code properly and improve error messages, but still it will be smal.

I compared speed with the Pro Solutions compiler on a 50Kbytes Protege
RDF-schema file (interpreted as RDF).  The Pro Solution compiler needs
3 seconds (PPro 200 running Linux).  The SWI-Prolog based one 0.41
seconds with quite some room for improvements.  It uses a high-level
description language and dedicated (bit still rather simple) compiler
to generate real Prolog.

Two new questions.  First looks like a bug in the 02/22 specs:

================================================================
<?xml version="1.0"?>

<!-- Example from REC-rdf-syntax, demonstrating abbrevation -->

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:s="http://description.org/schema/"
         xmlns:v="http://description.org/view/">
  <rdf:Description about="http://www.w3.org/Home/Lassila">
    <s:Creator>
      <!-- REC-rdf-syntax just says `about' -->
(*)   <s:Person rdf:about="http://www.w3.org/staffId/85740">
        <v:Name>Ora Lassila</v:Name>
	<v:Email>lassila@w3.org</v:Email>
      </s:Person>
    </s:Creator>
  </rdf:Description>
</rdf:RDF>
================================================================

In the (*) line, it says simply `about', but if I understand things
correctly this brings `about' in the `s' names space, resulting in
a quite different interpretation.  Right?

Second is again on the protertyElt production [6.12].

What is the difference between

  <rdf:Description ID="foo">
    <a1 ID="bar">
       <rdf:Description>
	  <name>Hello World</name>
       </rdf:Description>
    </a1>
  </rdf:Description>

and
      
  <rdf:Description ID="foo">
    <a1>
       <rdf:Description ID="bar">
	  <name>Hello World</name>
       </rdf:Description>
    </a1>
  </rdf:Description>

I have the impression they should be the same and specifying both ID's
inconsistent is an error.  Right?

	Regards --- Jan
Received on Wednesday, 26 April 2000 14:51:05 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:43 GMT