[OAI-implementers] Library of Congress announces standard MARCXML schema

herbert van de sompel herbertv@lanl.gov
Wed, 05 Jun 2002 08:37:35 -0600

hi all,

I would like to draw your attention to an interesting development that
is likely to impact certain OAI-PMH implementations.

As can be seen from the attached press release, the Library of Congress
has just announced an XML Schema for MARC 21 records.  As this will be
an authoritative Schema for MARC21 records, we will include it as a
recommendation in the Implementation Guidelines that come with OAI-PMH

Also, as a result of communications we had with the Library of Congress,
a conversion stylesheet is being provided that supports
transformation/migration from oai_marc to MARCXML.  It is available at
http://www.loc.gov/standards/marcxml/.  I would like to thank the
Library of Congress for providing this tool, recognizing the importance
of the installed base of OAI-PMH applications that have adopted


herbert van de sompel


Library of Congress announces standard MARCXML schema

The Library of Congress Network Development and MARC Standards Office
announces completion of a schema for MARC 21 records in an XML structure
for use in communicating MARC 21 records.  It is available from http:
www.loc.gov/marcxml.   This schema was developed in collaboration with
OCLC and RLG and reviewed by the National Library of Canada and the
National Library of Medicine (NLM), after a survey of schemas in use in
various projects.  Many schemas have taken the Aslim@ approach but all
vary slightly.  This schema will be maintained by the Library of
Congress as will software that enables lossless conversion to and from
MARC 21 records in the ISO 2709 structure.  As illustrated in the
introductory information on the web site, the Library of Congress will
develop and provide, downloadable from the MARCXML web site, tools for
various transformations and for record validations.  A single schema
serves all the five MARC 21 formats.

By collaboratively developing a communications schema, the Library of
Congress encourages the standardization of MARC 21 exchange records in
the XML environment, recognizing that  MARC 21 records inside systems
will continue to use different record configurations, tailored to the
characteristics of the system.  Provision of the tools for
transformations to and from other metadata approaches, such as Dublin
Core and the Metadata Object Description Schema (MODS), will help to
standardize derivative metadata records also.  (MODS is a new schema for
a bibliographic element set that is a subset of MARC expressed in XML
with language-based rather than numeric tags.)  The tools take the
mappings between MARC and other metadata sets, that have been maintained
on the MARC web site, to an operational level.

One project interested in a standard, lossless MARCXML schema is the
Open Archive Initiative (OAI) which found it necessary to draft a schema
in the absence of an official one.  The Library of Congress worked with
the OAI to provide a transformation from the original oai_marc schema to
this one so the Initiative can take advantage of a schema that is
maintained by the MARC 21 maintenance agency and in broad use.  The
transformation is available from the MARCXML web site.

With the slim approach, schema-driven validation is only possible at the
highest structural level.  The Network Development and MARC Standards
Office will therefore maintain downloadable tag, subfield, and value
validation software on the web site that will enable users to build
validation programs for their needs.  Use of these standard validations
represent another attempt to assure standardization of records to
support effective record interchange.

The Library has maintained two SGML DTDs (for Bibliographic-type and
Authority-type records) since 1996, which take a different approach to
the data elements in MARC B an approach that enables validation of data
through the DTD itself but requires a very large DTD and DTD
maintenance.  The Bibliographic-type DTD was converted to an XML DTD in
2000.  These DTDs have been effectively used by some agencies (including
the Library of Congress), primarily for internal processes, therefore
transformations between them and the new slim MARCXML schema are being
provided.  Maintenance techniques and/or possible revision of the XML
DTDs are under consideration.

For questions or comments please email the Office at ndmso@loc.gov.

Sally McCallum, Chief
Network Development and MARC Standards Office
Library of Congress, Washington DC, USA

Herbert Van de Sompel
digital library research & prototyping
Los Alamos National Laboratory - Research Library
+ 1 (505) 667 1267 / http://lib-www.lanl.gov/~herbertv/

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