Cataloguing according to RDA in MARC 21 format  Specification for local cataloguing practice of the CLB

In processing records, the CLB has long followed local processing standards to ensure homogeneity of data for retrieval and further processing. Since there is no satisfactory standard for processing analytical material at the national level, especially for retrospective excerpts and excerpts of specific types of material that are not practically dealt with by other departments (online documents, samizdat and exile material, analytical breakdown of book publications), and the processing of specialist subject bibliography requires more detailed and structured data entry than regular library cataloguing, the practice of processing CLB records differs in some respects from the RDA cataloguing rules introduced in the Czech environment in 2015. The cataloguing standards of the CLB have been continuously developed over a long period of time (cf. Macek 1969), the methodological basis for the processing of subject analytical bibliography is anchored in a certified methodology (cf. Malνnek 2015 and 2020), and current cataloguing practice is also mapped in continuously updated internal manuals.
The most important difference is that the source of the description for the CLB is the entire processed document, or any other relevant information about it from external sources (archival sources, etc.). The CLB therefore continues to use parenthetical additions to record the data supplied by the processor, as well as to use established conventional abbreviations: both to maintain homogeneous recording and to facilitate automated data processing. 

Overview of the differences in the entry of CLB data:
1) From MARC21 rules
* Linking to the authority base (set of national authorities) in subfield 7.
* Positions 1834 in field 008 are not used.
* Fields 100 and 110  the first indicator 0 is consistently used for ciphers, the source document is given in subfield c in [] to distinguish homonymous documents.
* Field 130  we do not create a main header for actions.
* Of the fields in block 5XX, only fields 500, 505 and 520 are used. The field 546 contains only historical data from the conversion and is not further supplemented.
* Field 506 contains non-public/internal notes.
* Field 600 is not used for the entry combining author and title of work (combination of subfields a+t), instead all parts data are entered in field 787.
* Field 630  only anonymous works with an authoritative record in the AUT database (otherwise field 787 is used; including works of other artistic genres).
* Block field 6XX  the refinement fields x, y, and z are not used.
* The x subfield in the 6XX block fields is used for an internal note for headings that are not linkable to the AUT database. 
* Field 653  used for occasional terms with an expected low frequency of occurrence.
* Field 700  so called analytical headers are not used.
* Field 787  consistently used for the entry of works without exception (instead of fields 600a+t and 630), subfield 4 characterises the type/genre of document; 
	- 2 fill types: 
		* work (FRBR-work, or FRBR-expression)  a+t+4; 
		* work as a specific manifestation (edition -> FRBR-manifestation) depending on the specific need; subfield n used to record responsibility data.

2) From national interpretation of MARC 21 rules
* Field 072 is always used just once.
* Field 080 for retroconverted records is used by the legacy MDT standard (referred to as "MRF-sel" in subfield 2).
* Subfield 245c  written according to AACR2 logic, i.e. including any parenthetical additions; the rule that information obtained from other than the source document/added by the processor is written in square brackets is consistently applied.
* Field 250  the abbreviation "ed." is used.
* Subfield 260a/264a  place of issue is normally written in the nominative case.
* Field 260/264  the abbreviations "b.m,", "b.n." and "b.d." are consistently used to record missing publisher information. 
* Field 300  values over and above the existing NL inventory are used; the field is used as repeatable; in the case of the Czech Literary Web Bibliography, data on the length of attached audiovisual files are systematically recorded.
* Subfield 490v  the entry uses conventional abbreviations (vol., Bd., etc.).
* Field 773  notation according to the local standard described in the methodology of processing the analytical bibliography, the punctuation and abbreviations used are described there; subfield g uses conventional abbreviations; subfields g, q and 9 are repeatable; the ANL-based interpretation is not sufficient for our needs.

3) Specification of local/national fields
* Field 524  contains an automatically generated document citation according to industry standards.
* Field 594  used to identify the variant of the person's name used and the associated preferred header.
* Field 599  an auxiliary field to identify the base.
* Field 910  the library sign of the processing institution is entered here.
* Field 961  action data (for converted records, not further expanded).
* Field 964  local base assignment data; for older converted records, subject classification codes (not further expanded).
* Field 990  link to another record.

4) Fields and subfields beyond MARC21
Aleph technical fields
* LKR field  specifies the linkage to another record.
* OWN field  used to separate the Aleph logical base.
* SIF field  identifies the processor of the record.
* CAT/KAT field  information about the change of the record (processor, time, etc.).
