This International Standard describes, in the form of a directory, data elements used to support the processes of acquisition, resource description and cataloguing, searching and requesting loan or copy by an end user or an institution. This International Standard includes data elements that are exchanged or are potentially exchanged among bibliographic systems. Those data elements that are not exchanged or not likely to be exchanged are ignored as they do not need standardization. Data elements being handled by transport protocols are not included, only those related to application level protocols. As part of the consolidation phase, the data elements were broadly classed and sub-classed and are presented in two sequences, one by class and sub-class and the other by an alphabetical sequence. The alphabetical sequence includes examples and synonyms identified during the consolidation phase and those found in related interchange protocols and schemas. As the grouping of data elements may differ among different protocols and record schemas, the data elements have been broadly classed and grouped, but no further structure has been made. Similarly, the sequence of data elements, whether or not a data element is mandatory or how it is structured and validated may vary according to its employment and consequently these data element attributes are outside the scope of this International Standard.