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 [email protected] 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 [log in to unmask]
Sally McCallum, Chief
Network Development and MARC Standards Office
Library of Congress, Washington DC, USA
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^ Rebecca S. Guenther ^^
^^ Senior Networking and Standards Specialist ^^
^^ Network Development and MARC Standards Office ^^
^^ 1st and Independence Ave. SE ^^
^^ Library of Congress ^^
^^ Washington, DC 20540-4402 ^^
^^ (202) 707-5092 (voice) (202) 707-0115 (FAX) ^^
^^ [log in to unmask] ^^
^^ ^^
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