xml-dev - RE: A certain difficulty

[Mark Birbeck <Mark.Birbeck@iedigital.net>]

David Megginson wrote:
> Mark Birbeck <Mark.Birbeck@iedigital.net> writes:
> > So, to illustrate, if today I want to see all documents 
> where "creator"
> > is David Bowie, then today I set "composer" and "author" 
> and "painter"
> > to be equivalent.
> 
> Actually, there should be no need to do anything like that.  I imagine
> a Web of objects (in RDF/DC or otherwise) would look something like
> this:
> 
>   <megg:Person rdf:about="http://megginson.com/objects/12345">
>     <dc:title>David Bowie</dc:title>
>     <dc:date>1947-01-08/</dc:date>
>   </megg:Person>
> 
>   <megg:Song rdf:about="http://megginson.com/objects/54321">
>     <dc:title>Space Oddity</dc:title>
>     <dc:date>1972</dc:date>
>     <dc:creator rdf:resource="http://megginson.com/objects/12345"/>
>   </megg:Song>

Yes but that's in your data universe. I'm looking at the situation where
I want to refer to other people's data.

Lets assume that your site has a massive database of every artist who
ever produced anything. My site though, might be only for classical
music. I might want to use a subset of your data, and I might want
people to search for 'Composer' rather than 'creator'. So I could set my
'Composer' class to be a sub-class of your 'Person' and, indicate that
valid values for the 'composed' property on a 'Composer' are objects of
the type of your 'Song':

<rdf:RDF
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 xmlns:rdfs="http://www.w3.org/TR/1999/PR-rdf-schema-19990303#"
>
	<rdfs:Class rdf:ID="Composer">
		<rdfs:subClassOf
rdf:resource="http://megginson.com/schemas/Person" />
		<rdfs:label>Composer</rdfs:label>
		<rdfs:comment>A writer of music</rdfs:comment>
	</rdfs:Class>

	<rdfs:Property rdf:ID="composed">
		<rdfs:domain rdf:resource="#Composer" />
		<rdfs:range
rdf:resource="http://megginson.com/schemas/Song" />
		<rdfs:label>composed</rdfs:label>
		<rdfs:comment>Piece that this composer
composed</rdfs:comment>
	</rdfs:Property>
</rdf:RDF>

The thrust of my argument is simply that it is going to be easier to
build systems that recognise the inherent dynamism of the web, than try
to enforce standard schemas.

> A composer is just the creator of a song, while a sculptor is the
> creator of a sculpture.  There's no need to define all of the things
> dc:creator can refer to, as long as you explain the kind of
> relationship it defines.

Hopefully my example shows that I'm coming at this from the other side;
*my* creator might be "everyone who has designed a building" whilst *my
mum's* creator is "everyone who has knitted a jumper". Of course we
could say everyone must use "dc:Creator", but then how do I find
everyone who ever knitted a jumper? Well of course I go to the knitting
site that has used RDF to refer to subsets of other data, because they
have a class called "Knitter".

Best regards,

Mark

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