I suspect, however, that the techniques used here and the patterns that are revealed will be the same in the authorities format. This analysis is currently limited to the MARC21 bibliographic format. The description of the MARC21 bibliographic format is available at, while the records in library catalogs that use this format are examples of instance data. To illustrate, the MARC21 field definition for an ISBN is tag 020 an instance of the ISBN would be the ISBN number itself tagged in a MARC21 record: 020 $a 0877790019. This analysis is intended solely to identify the bits of information that library data can contain. This mapping will not be sufficient to translate individual MARC21 records to a different format that would require further information that would need to be provided by one or more applications. The analysis here is an analysis of MARC21 format data elements, not of MARC21 instance data. That task, as Thomale evidenced in his example, is more difficult than it may seem.Ī few caveats are in order. It is therefore logical that a first step in the transformation of MARC21 to another format (or formats, for there may be more than one) is to identify the data elements that are contained within the MARC21 record. It takes only a short investigation of the data coded in MARC21 to reveal that the tags and subfields themselves are inadequate to define the actual data elements carried in library catalog records, as Jason Thomale discussed in his recent article. What these questions do not address is the much more difficult task of translating the semantics of library data into something new.

Discussions about this tend to focus on structural issues: will the new format be an XML format? Will it make use of RDF and linked data standards?

In the library community there is a growing recognition that there will need to be a successor to the MARC21 bibliographic format.

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