MARC (General Overview)

Within this report we investigate selected MARC formats which are of interest in the context of the study. This entry provides some general context for other entries (USMARC, UNIMARC, UKMARC).

Environment of use

Constituency of use

MARC (Machine Readable Catalogue Format) originated in the 1960s as a means of exchanging library catalogue records. MARC was a response to the need for a standardised format for co-operating libraries to exchange and share catalogue records. It also met the requirements of national bibliographies for a format for their printed bibliographies, and it was used by bibliographic agencies for their supply of records to libraries. As library systems became computerised, MARC was used in library automation software as the basis for manipulating library records for display and indexing.

As use of MARC became more widespread the format was developed and adapted by its various user organisations and institutions according to their own disparate requirements. So, for instance, national libraries have tended to develop national MARC formats suitable for the material types they themselves catalogue (e.g. USMARC historically has included differing formats according to the requirements of the Library of Congress); library automation systems have developed MARC variants according to the needs of their users (e.g. the UK library management system vendors SLS and BLCMP use variants of UKMARC); adjustments for multilingual and cultural requirements have led to other formats (e.g. IBERMARC, CATMARC).

MARC format provides a means of integrating metadata into existing systems. National bibliographies, bibliographic record supply agencies, and individual libraries all have large collections of existing MARC records and want to integrate 'Internet descriptions' into their systems, and for them MARC is an obvious choice as it means their basic retrieval software can still be used to offer an integrated solution

The problem is that there is a considerable timelag between changes to the MARC format and changes appearing on the libray's OPAC, as this requires upgrades to the library's existing library management software.

Documentation

The proliferation of MARC formats was possible because the 'MARC standard' ISO 2709 Format for bibliographic information interchange on magnetic tape only governs record structure or encoding, it does not prescribe the content of the record within that structure. The record content of different MARC formats is defined in 'de facto' standards, usually controlled by national libraries; these take the form of cataloguing manuals outlining the formats and offering guidelines for their use.

Progress towards international standardisation

There is a move towards convergence of MARC formats: English speaking countries are converging to USMARC; European countries are looking to UNIMARC to map divergent MARC formats.

Convergence of other national MARC formats with USMARC mean that developments within USMARC are becoming increasingly influential. The critical mass of libraries using this format mean that it is possible for projects such as Intercat to find interested participants. The large numbers of USMARC users could be used as leverage with library automation system vendors for inclusion of format changes to be applied in OPACs, although this is an outstanding problem for Intercat participants.

Ease of creation

The creation of high quality MARC records requires training and experience in the use of cataloguing rules. Although the input of data to a record can be automated, the cataloguer needs to view the resource in some detail, and then interpret cataloguing rules before formatting the required information correctly in the MARC record. Within libraries specialist staff are assigned to cataloguing, they are often familiar with only one national format and indeed often specialise by material type (e.g. by subject area or format).

Format issues

Encoding

ISO 2709 states that a MARC record must consist of variable length fields with content designators; the record should have a record label, a directory, data field separators and record separators. Within these constraints different implementations of the standard have used different numbered tags and different subfield codes to identify the same type of bibliographic data.

The standard allows for optional indicators to appear after the tag and these are used in many MARC formats to qualify the tag. Within the text of a record, embedded subfield identifiers can be used to further identify data elements. ISO 2709 allows for fixed length data as part of the record label and this is used to store codes relating to material type, language, dates and so on.

Protocol issues

The Z39.50 protocol which enables search and retrieval of bibliographic information over the Internet is particularly designed to accommodate the search and retrieval of MARC records. The protocol can be used to pass searches of MARC fields from a Z39.50 client to a Z39.50 server fronting a databases of MARC records; and retrieved records can be returned in MARC format. The Z39.50 protocol uses attributes to identify how search terms should be treated by the server in a search. The bib-1 attribute set is defined in the standard and within that set the 'Use Attributes' were designed to map onto bibliographic records such as MARC. The bib-1 Use Attribute set does not contain any location or other non-bibliographic data so it is not possible to search on these fields. The protocol does allow for delivery of MARC records in full or abridged versions. There is no attempt in the standard to identify whether records searched or delivered are in the US or UK or other MARC formats. This can cause problems for interoperability in, for example, author personal name searches where the name is stored differently in US and UK MARC; similarly because the 'flavour' of MARC format is not identified it is not easy for the client to vary the display depending on the MARC format of the retrieved records. The standard allows for delivery of holdings information in OPAC records. At present the electronic address (and other non-bibliographic information) is not part of the bib-1 attribute set and is not searchable, however it would be displayed in a retrieved MARC record.

The majority of library automation systems allow for input and retrieval in MARC format, even if the records are stored internally in another format. Any changes in MARC, particularly regarding the display of the 856 field, will need to be reflected in OPAC software.

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