Bibliographic data formats

Bibliographic data formats adopted for exchange of data consist of three basic components: 

1. A defined physical structure: Rules for the arrangement (on a computer storage medium) of data to be exchanged. This may be linked to a container or carrier into which data may he placed. The carrier remains constant although the data change from record to record. 
2. Content designators: Codes to identify the different data elements in the record (e.g., author, title, scale of map, starting date of journal, etc.) 
3. Rules: Content of the record governed by rules for the formulation of the different data elements, very closely tied up with 2 above. The data elements separately identified by the codes in the exchange format have to be defined, not only in terms of content but also in form, if the records are to be suitable for use by another agency.