On Wed, 19 May 1999, Gisle Hannemyr wrote:
> <?xml version="1.0"?>
> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> xmlns:dc="http://purl.org/dc/elements/1.0/"
> xmlns:dcq="http://purl.org/dc/qualifiers/1.0/">
> <rdf:Description about="http://my page/">
> <dc:creator>
> <rdf:Description>
> <rdf:value> Jim Weinheimer </rdf:value>
> <dcq:creatorType
> rdf:resource="http://my schema/creatortype/Princeton_Librarian#"
> />
> </rdf:Description>
> </dc:creator>
> </rdf:Description>
> </rdf:RDF>
>
> Now, when our DC-conscious web-crawler stumbles across this
> revised version, it would probably think something like:
> 'dc="http://purl.org/dc/elements/1.0/", well I guess I better pay
> attention! And dcq="http://purl.org/dc/qualifiers/1.0/" as well,
> oh my, oh my!'
> and then it would start parsing the page.
>
> Going into the process in more detail, the web crawler would
> proceed to mumble to itself:
> 'So it's this "Jim Weinheimer" entity wot's the creator of this
> resource. That's nice.',
> and then it would proceed to examine the element qualifier
> (i.e. the dcq:creatorType part), and unless somebody has done a
> lot of very hard work in making automatic recognision of
> arbritrary defined schemas avilable, it would go on like this:
> 'Well if I had been a whole lot more clever I've would have been
> able to make sense of the macine readable schema specification
> that live on the address "http://my
> schema/creatortype/Princeton_Librarian#".
> But I don't.';
> and then it would mumble "Hasta la vista, baby" in an Austraian accent,
> and be gone.
>
> How much is gained by having the qualifier defined like this.
> Not very much (IMHO). But it gets worse.
You are basing this on a 'dumb-down rule' that hasn't been published
ouside of the DC-Datamodel WG and that probably needs more work. For
example, the rule could say that DC engines throw away the rdf:value if
the dcq:creatorType isn't a recognised DC Type. This whole area needs
more work.
> Now, let us assume that somebody think that the following is a great
> way to tell the world about the birthdate of the creator of the
> resource:
>
> <?xml version="1.0"?>
> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> xmlns:dc="http://purl.org/dc/elements/1.0/"
> xmlns:dcq="http://purl.org/dc/qualifiers/1.0/">
> <rdf:Description about="http://my page/">
> <dc:creator>
> <rdf:Description>
> <rdf:value> 1953-07-13 </rdf:value>
> <dcq:creatorType
> rdf:resource="http://my
> schema/creatortype/PersonalName/DateofBirth#" />
> </rdf:Description>
> </dc:creator>
> </rdf:Description>
> </rdf:RDF>
>
>
> Oh yes, this is valid Qualified Dublin Core. If we accept Qualified
> Dublin Core, there is nothing (reapeat nothing) to stop people from
> doing this.
>
> Will they do this?
> You bet!
This example may be valid syntax for qualified DC. But it doesn't mean
anything, because DateofBirth doesn't refine the semantics of the
dc:creator property in any meaningful way. (In DC Datamodel terms,
DateofBirth is a value component not an element qualifier).
So, if someone chooses to do this, they will have metadata that doesn't
mean what it says and that doesn't interoperate with anyone else (or that
only interoperates with people who have a shared local agreement to
mis-use the model). So what! There are umpteen ways in which people can
create metadata that doesn't interoperate? If people want to interoperate
then they will have to create metadata according to rules - and the rules
will include syntax rules and cataloguing rules.
Andy.
--
UK Office for Library and Information Networking
University of Bath, Bath, BA2 7AY, UK Voice: +44 1225 323933
http://www.ukoln.ac.uk/ukoln/staff/a.powell/ Fax: +44 1225 826838
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