MEG Metadata Schemas Registry
Creating and Registering schemas : a practical workshop
UKOLN, University of Bath, 21 Jan 2003

Background:
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Schema registries are an attempt to enhance interoperability in a world
where MARC no longer has a monopoly on how metadata is represented and
transfered. The idea is to recognise that while most developers of resource
discovery services are keen to interoperate they want to use resource
descriptions which are tailored for their communities/resource types. The
idea is that these developers would be able to re-use elements from
existing resource description schemas.


Definitions:
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I found the definitions of terms used in the workshop to be useful, and so
will repeat them here:

Element set: a coherent bounded set of terms formulated as a basis for
metadata creation. These are designed for a particular purpose (eg
describing learning objects) and maintained by a designated agent. Examples
are Dublin Core elements and refinements, MARC, IEEE LOM, GILS, MPEG-7 vCard.

Application Profile: an element set optimised for a particular local
application. It may draw elements from one or more element sets.

Schema: a structured representation that defines and identifies the data
elements in an element set.

Pete Johnston distinguished between elements and element usages where an
element usage is the deployment of an element in the context of a
particular domain or application. An element usage might refine or
narrow the semantics of an element from an element set, it may specify
cardinality constraints, and it may associate an element with specified
encoding schemes. An application profile is thus a set element usages
(remebering that within an application profile, the "used" elements may be
drawn from several different element sets).


The Registry
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The MEG Schema registry uses a client-server model. The server side accepts
machine readable schemas which are stored in RDF, indexes these, provides a
search/browse interface for human readers (HTML) and software tools.
Information on Agencies (people / organisations responsible for element
sets and application profiles), element sets, elements, encoding schemes
(eg iso 3166 country codes) and values in encoding schemes, element usages
and appliction profiles.

In the workshop we had the opportunity to use the registry to enter our own
  application profiles. This prove easier for application profiles based on
Dublin Core than it was for the LOM. There was plenty of discussion about
whether this was a fundamental mismatch in the models used by the registry
and the LOM, or whether it was simply a reflection of the LOM being more
complicated than Dublin Core. A complicating factor is that the registry
uses ideas from RDF, and the RDF binding for the LOM is not yet complete.
It will probably be the case that viewing the LOM through a system based on
RDF will provide insight into the semantics of the LOM which are not
obvious from the information model.


For more information see the MEG Registry project web page at
http://www.ukoln.ac.uk/metadata/education/regproj/, or contact Pete
Johnston <url: http://www.ukoln.ac.uk/ukoln/staff/p.johnston/>

Thanks to Pete, Rachel Heery and all those at UKOLN for providing an
opportunity to learn more about this project.


--
Phil Barker                            Learning Technology Advisor
      ICBL, School of Mathematical and Computer Sciences
      Mountbatten Building, Heriot-Watt University,
      Edinburgh, EH14 4AS
      Tel: 0131 451 3278    Fax: 0131 451 3327
      Web: http://www.icbl.hw.ac.uk/~philb/