Andy,
I am currently working on an XML Schema for UK LOM CORE that
does not mandate any elements, but uses Schematron to produce a report
on whether the record conforms to the UK LOM CORE recommendations.
The reason for this approach is that you do not need to use
advanced features of XML Schema to ensure uniqueness of top level
elements etc but still get the information as to whether the record
conforms.
I hope to have a version of this done within the next two weeks
and I will post it on the list.
Further developments will allow the selection of vocabularies
and (hopefully) a nice and friendly tool to do the processing.
Regards,
Ben
---------------------------------
Dr Ben Ryan
HLSI Software Development Manager
University of Huddersfield
Tel: 01484 473587
E-mail: [log in to unmask]
---------------------------------
-----Original Message-----
From: Andy Powell [mailto:[log in to unmask]]
Sent: 14 July 2004 16:17
To: [log in to unmask]
Subject: Re: UK LOM Core: mandatory elements
On Wed, 14 Jul 2004, Scott Wilson wrote:
> > But yes, something I was turning over after reading Andy's initial
> > message on this thread (and which I think is also touched on in John
> > Casey's comment about a repository requiring the "full monty" and
> > Scott Wilson's comment on "prior agreement" about data exchanged
> > between
> > services) is whether there is a potential tension here between the
> > requirements/preferences of a (in OAI-PMH terms) "data provider"
(the
> > agent who provides/exposes metadata) - "you can't really expect me
to
> > provide *all* this stuff!" - and those of a "service provider" that
uses
> > that metadata as the basis of a new service - "I'd really quite like
to
> > rely on having present all those elements that UK LOM Core says is
> > mandatory".
> >
> > I don't have an answer for how to resolve that tension! ;-)
>
> In Z39.50 world, this is what the "Explain" request is for - in Web
> Services this is the function of WSDL.
Unfortunately these methods only tell you some of the information that
you need to know. For example, Explain can be used by the client to find
out what search parameters are supported and what record formats are
available to be returned - but it won't tell you anything about the
rules that have been used to create the fields in those records. So you
can tell that a MARC record will be returned, but you can't tell if the
MARC record was created in accordance with AACR2 cataloguing rules.
Similarly, in OAI, the service provider can ask the data provider what
metadata prefixes are supported, and as part of the response to that
request, information about which XML schema is being used is passed
back.
So, if there was an XML schema for, say, RLLOMAP, a service provider
could
1) prior to beginning harvesting, determine if the records available
from the data provider are likely to be useful in terms of containing
the correct elements and so on (but not in terms of whether particular
values have been constructed according to particular rules).
2) validate individual records as they are harvested and reject ones
that didn't contain mandatory fields.
*But*, we don't currently have an XML schema for UK LOM Core or RLLOMAP
- we just use the standard LOM schema - so we can't do any UK LOM Core
or RLLOMAP specific validation. And, more importantly, such validation
wouldn't tell us anything useful about what rules were used by the
cataloguer when the metadata fields were created.
I still think we need to ask oursleves questions like "What is the
purpose of an application profile?", "What does XML Schema already give
us that we don't need to replicate in the application profile?", "What
does mandatory mean?" and "What are the benefits and downsides of making
particular elements mandatory or not?".
My personal opinion is that the real benefit of something like UK LOM
Core is in achieving greater (but not 100%) consistency in the choice of
metadata elements and the way values are constructed for those elements
across a range of disperate data providers - not about telling consumers
of metadata records from those services which elements will absolutely,
definately be available. So, as the developer of a metadata harvester,
the UK LOM Core doesn't need to tell me with cast iron certaintly that
every metadata record is going to contain 4.2 technical.size for
example, but it should tell me that if the record contains that element
then the value will be constructed according to the following rule -
"size in bytes (a number)".
If my application absolutely needs 4.2 technical.size in order to
function properly, then I can simply throw any records without that
element away. I don't need an application profile to enable me to do
that - I just do it, having looked at each record. But I do need the
application profile in order to make sure that everyone constructs the
value in the same way.
Andy
--
Distributed Systems, UKOLN, University of Bath, Bath, BA2 7AY, UK
http://www.ukoln.ac.uk/ukoln/staff/a.powell +44 1225 383933
Resource Discovery Network http://www.rdn.ac.uk/
ECDL 2004, Bath, UK - 12-17 Sept 2004 - http://www.ecdl2004.org/
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