---------- Forwarded message ----------
Date: Tue, 4 Jun 2002 16:20:29 -0400
From: Sally Hart McCallum <[log in to unmask]>
Reply-To: MARC <[log in to unmask]>
To: [log in to unmask]
Subject: Standard XML schema for MARC 21
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
"slim" 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 - 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]
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