Sirje Nilbe, National Library of Estonia
Abstract
The core of an OPAC is the database which usually includes data of three types - the bibliographic records, the authority records, and the indexes.
The bibliographic records are created according to the cataloguing rules like ISBD and AACR2, and formatted for computer processing according to the particular bibliographic format like USMARC or UNIMARC. The authority records serve for authority control by cataloguing and searching. They are created according to the MARC formats for authority data compatible with corresponding bibliographic formats. The general form for indexes in a bibliographic database is an inverted file including the access points to the records and the pointers referring to the relevant records.
In the paper an introduction to the MARC, authority control and computer-based database indexing is provided.