[OAI-implementers] XML Schema

Carl Lagoze lagoze@cs.cornell.edu
Sat, 8 Dec 2001 12:39:50 -0500

Tim,  I wish I could point you to one consise resource that explains the
details of all of XML namespaces, schema, etc., but no one stands out
for me.  Perhaps someone on the list has in mind something of that sort.

As to a brief explanation of how to specify metadata is marked up:

If you look at the OAI protocol spec you will notice the use of the
xsi:schemaLocation tag, which as a value that is a pair.  The first
element of the pair is a namespace URI and the second is the URL of an
xsd (xml schema) file.  This specifies that the data (content)
associated with the namespace is marked up according to the rules
specified in the schema.  You are correct that there is no assurance
that the contents of the schema will not change causing serious
breakage.  Also, the notion that all metadata must conform to a specific
data format (defined in a single schema) is not covered and may actually
not be a good idea.  In bibliographic terms, think of the namespace
notion as identifying a "work", which can have numerous schema
expressing the form of "manifestations" that are realized in individual
metadata "items" that match the schema.

hope this helps.


> -----Original Message-----
> From: Tim Brody [mailto:tim@tim.brody.btinternet.co.uk]
> Sent: Saturday, December 08, 2001 8:53 AM
> To: Carl Lagoze
> Subject: Re: [OAI-implementers] XML Schema
> > (foo, http://foometa.org/foo.xsd, http://foometa.org/foo#) should
> > interpret this as:
> >
> > "This server locally uses the name foo to indicate the 
> metadata concept
> > globally known as http://foometa.org/foo# and marks up 
> instance data for
> > the metadata concept foo according to the rules defined by
> > http://foometa.org/foo.xsd."
> >
> > Another server may return:
> >
> > (fooalt, http://altfoometa.org/fooall.xsd, http://foometa.org/foo#)
> > indicating a different markup of the same metadata concept.
> Hi,
> Could someone explain this a bit further or point me at an appropriate
> resource. What does someone have to do, with XML, to be able 
> to identify how
> metadata is marked-up? I am guessing you have to use the string
> "http://whatever/foo.xsd", but surely the metadata schema can 
> be changed
> (which would break everything)?
> All the best,
> Tim.