With regard to Dublin Core, one solution to defining which metadata
elements may occur in a particular recordSchema is through the use of an
application profile. An application profile includes Dublin Core
elements, but at the same time may include elements drawn from other
namespaces to meet needs not covered by DC.

There are proposals to standardise the description of DC Application
Profiles and perhaps that approach could be used to describe the formats
returned by SRU - well at least the ones based on DC.

It is possible that a recordSchema can conform to a number of profiles.
Perhaps the Explain schema could be extended to allow an indication of
the Application profile supported by a particular recordSchema and
client software could use this information to decide which recordSchema
to request.

There are a lot of dependencies to be resolved before this would work,
but it does seem a reasonable path to pursue.

Bill

-----Original Message-----
From: Z39.50 Next-Generation Initiative [mailto:[log in to unmask]] On Behalf
Of Theo van Veen
Sent: 11 August 2005 09:17
To: [log in to unmask]
Subject: Re: An alternative to complex record containers

>>> [log in to unmask] 11-08-2005 4:04 >>>

I do not see the actual difference between

<dc:dateCreated xsi:type="ISO8601">2001-01-01</dc:date.created>
and
<element id="DC.Date.created" encoding="ISO8601">2001-01-01</element>

The first one is according to the DCMI guidelines for encoding dc in
XML which I think we should follow as much as possible.  However DCMI
defines the terms and not the structure of the record where these terms
are part of. It is also valid to add other elements from other
namespaces. Therefore DCMI allows a lot of flexibility and freedom. For
what you are trying to do I would advide you to use RDF according to the
DCMI guidelines.

The main problem is how we deal with schemas. An XML schema which is
useful at the time of creation of metadata doesn't have to be meaningful
at the time of search and retrieval. At the time of search and retrieval
it might be enough that the record contains for example a title and a
resolvable identifier, while at the time of creation one may validate
for example against controlled vocabulaires for specific subject
headings. Therefor I think that the schema used for local validation is
not relevant for the outside world. Besides that there can be 1000 s.
For specification of what a record actually means for the outside world
we need a common schema which defines common elements.
I think that the different opinions in this group relate mainly to the
amount of freedom that a schema allows and we need to find a reasonable
compromise between "ending up with thousands of different restrictive
schemas that all are doing about the same"  and  "having a single schema
that has no restriction at all".

Theo

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