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Metadata Formats

for libraries through the creation of more formal standards to govern the
input of data into Dublin Core, but this level of flexibility is still viewed as
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a fundamental weakness within the schema.

MODS

Given the large quantity of metadata, workflows, and knowledge tied up
in the development of bibliographic data such as MARC, the question of
how these legacy records and systems will be moved towards a more XML-
centric metadata schema is an important one. In the mid-1990s, the Library
of Congress took an important first step by offering an XML version of
MARC in MARC21XML. As noted above, MARC21XML was developed
to be MARC, but also in XML. It represented a lossless XML format for
MARC data, with many of the benefits of XML while at the same time being
inhibited by the technical limitations of MARC.

History
Unfortunately, MARC21XML has had little uptake from the metadata com-
munity. While benefits exist to using MARC21XML over traditional MARC,
few library systems have made the move to support MARC21XML as an
ingestible metadata format. Given this fact, the usage of MARC21XML has
been primarily by library developers creating custom applications for their
own local use.
In part, MARC21XML likely didn’t catch on as a popular library meta-
data format precisely because it was so tied to traditional MARC. For many,
MARC and the rules governing it had simply become too archaic. MARC
was developed for a time when bibliographic data was printed on catalog
cards, and the move to an XML-based metadata schema represented a
chance to break away from that bibliographic model.
For its part, the Library of Congress recognized the need within the
library community for a metadata schema that would be compatible with the
library community’s legacy MARC data, while providing a new way of rep-
resenting and grouping bibliographic data. These efforts led to the develop-
ment of the MODS (Metadata Object Description Schema) metadata format.
MODS represents the next natural step in the evolution of MARC into XML.
MODS represents a much simpler alternative that retains its compatibility
with MARC. Developed as a subset of the current MARC21 specification,
MODS was created as a richer alternative to other metadata schemas like
Dublin Core. However, unlike MARC21XML, which faithfully transferred
MARC structures into XML, the structure of MODS allowed for metadata
elements to be regrouped and reorganized within a metadata record.
As seen in figure 6.7, another major difference between MODS and
MARC and MARC21XML is the use of textual field labels rather than
numeric fields. This change allows MODS records to be more readable
than a traditional MARC/MARC21XML record, and it allows for element
descriptions that can be reused throughout the metadata schema. A number

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