In catalogue entries we not only provide for access points to meet the variety of user needs to find a document but also information about the document. The information we give in the main entry will help the user form an idea as to the nature and the contents of the document. Users will, thus, be able to decide the usefulness or otherwise of a document in the particular context of their requirements.
At the same time we cannot overdo in providing information by giving every possible detail. Therefore, a catalogue code speaks of the extent of information to be given in a catalogue entry - main or added. It names the various parts of the entries and the type of information given in each part.
Each part contains certain elements of information. For example, the part known as 'Title and Responsibility' part contains information on the title of the work; its sub-title if there is a sub-title; alternative title when the work is in a different language. Similarly, this part also gives information about the author or authors and other collaborators responsible for the work.
The different elements that provide information about the document in the catalogue entry are the data elements. A group of data elements arranged in a prescribed order constitutes an area of description. In a part of a main entry sometimes there may be two or more areas of description.