[rak-list] (Fwd) Standard XML schema for MARC 21

[Bernhard Eversberg]

Hallo Listen,

soeben wurde bekanntgegeben, dass die LC eine XML-Implementierung von MARC21 
verabschiedet hat. Die Dokumentation findet man unter
http://www.loc.gov/marcxml
Dies bedeutet NICHT, dass MARC21 durch XML abgeloest wird, sondern alle MARC-
Tags, subfield codes und Indicatoren bleiben unveraendert erhalten, sie werden 
nur in XML eingebettet. Es geht bei dem XML-Schema nur um die Syntax dieser 
Einbettung, nicht um irgendwelche Veraenderungen an MARC21 selbst. Man spricht von
"roundtripability", d.h. Umwandlung von der alten in die neue Struktur und 
zurueck ist verlustfrei moeglich.
Der Preis ist ein Speicherplatz-Mehrbedarf: wo das alte MARC diese hat:
260   $aNew York$bH. Holt$cc1988
da sieht es nun so aus:
<datafield tag="260" ind1="" ind2="">
  <subfield code="a">New York :</subfield> 
  <subfield code="b">H. Holt,</subfield> 
  <subfield code="c">c1988.</subfield> 
</datafield>
Das sind 178  statt 34 Byte oder 520% des alten Volumens.
Daher wird niemand diese Struktur datenbankintern verwenden wollen, wofuer sie 
aber auch nicht gedacht ist. Es geht um Datenaustausch, nichts anderes.

Es folgt die Originalnachricht:

------- Forwarded message follows -------
Date sent:      	Tue, 4 Jun 2002 16:20:29 -0400
Send reply to:  	MARC <MARC at loc.gov>
From:           	Sally Hart McCallum <smcc at loc.gov>
Subject:        	Standard XML schema for MARC 21
To:             	MARC at sun8.LOC.GOV

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 ndmso at loc.gov.
------- End of forwarded message -------

Bernhard Eversberg
Universitaetsbibliothek, Postf. 3329, 
D-38023 Braunschweig, Germany
Tel.  +49 531 391-5026 , -5011 , FAX  -5836
e-mail  B.Eversberg at tu-bs.de