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RDF and recipes

From: Aaron Straup Cope <asc@vineyard.net>
Date: Mon, 28 Apr 2003 08:19:08 -0400 (EDT)
To: www-rdf-interest@w3.org
Message-ID: <20030428080636.B44631-100000@king1.vineyard.net>

Hello everyone,

My name is Aaron and a while back I wrote myself an XML application for
describing recipes, meal courses and menus:


The DTD is not, as far as I know, RDF-friendly though I have been
considering making it so.

To be frank, I have doubts about the actual viability of RDF outside of a
limited set of applications. But I can imagine my recipe DTD might be one
of them so I'd like to spend a little more time investigating what changes
are necessary to make my thingy play nicely with all the other RDF

I have two basic questions. One is straightforward, the other not so much.

1) I read once that the RDF/XML spec would not allow for the use of
XInclude data. Is this true? Has it been corrected?

2) This question essentially boils down to: where does the data stop and
the meta-data begin?

I have included (below) snippets from a conversation I had with Karl
Dubost on the subject which goes on to ask some basic technical questions
about one actually uses RDF.

Any input would be very much appreciated. Thanks,


Anyway, humour me and tell me which part of the following is data and
which part is meta-data:

   <quantity><n type = "int" value = "1" /></quantity>
    <unit content = "teaspoon" />
  <item>vanilla extract</item>

On Wed, 9 Apr 2003, Karl Dubost wrote:

> If you look at it for the cooking aspect and only in this abstract.
>       + type of ingredient is an interesting data
>       in this case the type of ingredient has for value "Vanilla"
> Because for example I want a meal tonight with the flavour of Vanilla.

But the flavour of vanilla isn't vanilla extract, nor is vanilla extract
vanilla. And it's unclear why I should include that kind of meta-data in a

This presumably is where we start getting into the high weirdness
surrounding RDF classes?

I can imagine how to express this using an OOP (perl) model but I have no
idea how you're supposed to do it in RDF and what you're actually supposed
to include in the data-file itself...

package Vanilla;

sub taste { "smooth"; }
sub form  { "solid" }

package Vanilla::Extract;
use base qw (Vanilla);

sub form { "liquid" }

---------- Forwarded message ----------
Date: Wed, 9 Apr 2003 13:17:41 -0400 (EDT)
From: Aaron Straup Cope <asc@vineyard.net>
To: Karl Dubost
Subject: Re: FYI: RDF and resto

On Wed, 9 Apr 2003, Aaron Straup Cope wrote:

> I can imagine how to express this using an OOP (perl) model but I have no
> idea how you're supposed to do it in RDF and what you're actually supposed
> to include in the data-file itself...

I gather it would be something like this...

   <rdfs:Class rdf:ID="Food">
     <rdfs:comment>Generic Food Class</rdfs:comment>
     <rdfs:subClassOf rdf:resource=

   <rdfs:Class rdf:ID="Vanilla">
     <rdfs:comment>Vanilla Class</rdfs:comment>
     <rdfs:subClassOf rdf:resource="#Food"/>

   <rdfs:Class rdf:ID="Vanilla_extract">
     <rdfs:comment>Vanilla extract Class</rdfs:comment>
     <rdfs:subClassOf rdf:resource="#Vanilla"/>

   <rdf:Property rdf:ID="form">
      <rdfs:comment>The physical characteristics of a food item</rdfs:comment>
      <rdfs:domain rdf:resource="#Food"/>
      <rdfs:range rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Literal"/>

   <rdf:Description ID="solid">
    <rdf:type resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Property"/>
    <rdfs:subPropertyOf rdf:resource="#form"/>

   <rdf:Description ID="liquid">
    <rdf:type resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Property"/>
    <rdfs:subPropertyOf rdf:resource="#form"/>

...but it's unclear how I would write (in rdf-friendly XML) :

  <item>vanilla extract</item>

or even :

  the <form> of <vanilla extract> is <liquid>

or whether 'solid' and 'liquid' should be classes or descriptions and
whether one has any impact on multiple inheritance (multiple instances of

Never mind how much other verbiage I would need to define this particular
liquid as being "wet"; it is arguable that mercury isn't exactly wet
despite it's liquidity. [ed: not to mention financial liquidity]
Received on Monday, 28 April 2003 08:22:45 UTC

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