UNIMARC-The UNIMARC format

The UNIMARC format

The UNIMARC format, like any other version of MARC, involves three elements of the bibliographic record:

• Record structure
• Content designation
• Data content

Record structure

The record structure is designed to control the representation of data by storing it in the form of strings of characters known as fields.
All data in the record must be stored using one or more character sets. Since computers can store and manipulate only numbers, each symbol, alphabetical character etc. is assigned a number following the rules of a particular character set. For example, one character set assigns the number '75' to 'K'. UNIMARC allows the use of certain character sets, approved by the International Organization for Standardization (ISO).
The record structure established by UNIMARC is an implementation of the relevant standard:Format for bibliographic information interchange on magnetic tape (ISO 2709-1981). This structure utilises record labels and directories. As few users need concern themselves with such items, the description below covers the way a cataloguer sees the record.

Content designation

Certain conventions are followed in order to identify the data elements within records. Such elements which include author, title and subject access are further characterised where necessary. This supports the manipulation of the data for a variety of purposes:

• To provide multiple access points for searching,
• To allow the typography and layout to be varied,
• To permit certain elements of the record to be omitted where this is required.

For an example of such manipulation, see the "Displaying citations" section later in this document.
In addition, UNIMARC records may be formatted for visual display on a VDU, for output on CD-ROM or fiche and for printing out as hard copy.
In general, UNIMARC provides content designation only for data which is applicable to all copies of a work. However, information which applies only to some copies (or even a single copy) of a work may be of interest beyond the holding institution. In such cases UNIMARC assigns specific fields for such details. These fields are also available for cases where the information is for in-house purposes only.

Data content

The content is the data which is stored in the fields within the record. Data can be coded data or bibliographic data.

• Coded data is used to represent such items as control numbers, publication type, and main language of text. There is also provision for the characteristics of special types of items such as printed music.
• Bibliographic data is defined by reference to the International Standard Bibliographic Description for that type of material. In addition, each record can carry a class number and subject headings.

The purpose of UNIMARC, therefore, is to facilitate the description, retrieval and control of bibliographic items. This is achieved by providing a structure for recording bibliographic information which is input by reference to international standards.