Several non-MARC 21 and non-OCLC MARC 21 fields are necessary for a CBS:
- System fields, i.e. fields that are so important for the CBS software and configuration that they need to be part of the format when we use CBS MARC 21 as the cataloguing and database format in a CBS MARC 21 database.
- PICA fields, i.e. fields for which (at the moment) no MARC 21 and OCLC MARC 21 equivalents exist, e.g. tags that are used to be able to generate family presentations of title records and of authority records; or tags for indicating the ownership and shelf marks of special materials like old printed books, iconographic material, manuscripts and letters.
The PICA+ tags in the 001*, 101* and 201* ranges are reserved for real system tags.
Structure of CBS fields
We call both types of tags CBS fields. The CBS fields consist of 4 digits and the tag numbers are very logical. Tags starting with 0 apply to the main/master level, with 1 to the local/LBD level, and with “2” to the copy/holdings level. The only exception is tag H***, Holding header field, in the cataloguing format for indicating the start of a copy block. E.g. tag H001 is the start of the first copy block.
At the moment, the CBS MARC 21 authority format uses the levels main/master and local only.
Import and export of MARC 21 records
The non-MARC 21 and non-OCLC MARC tags are no part of the MARC 21 format, so they are not exported from a CBS to WorldCat. When importing MARC records into a CBS MARC 21 database, it is important to be aware of the (mandatory) non-MARC 21 and non-OCLC MARC 21 tags.
Filter or protect fields
In a CBS, you have the options to filter or to protect fields.
- Filtering means that the tags are stored in the database, but are not displayed in standard displays like the labelled and the MARC 21 display. Tags that are part of coded data templates may not be filtered by the filter configuration files; those tags are filtered by the software related to the coded data templates.
- Protecting means that a tag is displayed, but cannot be edited.
Only when you have system administrator rights, tags are not filtered nor protected.
Points of interest
- Tags that are filtered, are not "seen" by the semantic validation, when a record is cataloged, but during the import process it is or can be useful to validate these tags.
- Tags that are system tags are not validated (in principle).
- Tags that are non-system tags are validated although these tags may be protected, so it is important to check these tags during the import phase.