The preceding chapters have been mainly concerned with how the subject headings are presented, and what form they take. The form of headings is decided by the Policy and Standards Division of the Library of Congress, and you as cataloguer don't have any control over this; individual headings must be used consistently by everyone, both at the local level to ensure efficient retrieval, and across institutions to support the exchange of information and interoperability of catalogues.

In selecting headings for individual documents, however, you have much more freedom to do as you think best for your own situation. In this and the following chapter we shall look at how to choose headings in order to represent documents accurately and in a manner useful to end-users.

Before you can do that it is necessary to decide what the item being cata - logued is about. Whatever system of subject headings (or classification scheme or thesaurus) is being used to describe a document, you should try initially to make an independent assessment of what the subject of that document is. In practice, you will almost certainly be unable to represent this exactly using the artificial language of your system, but you should at least begin by deciding objectively what it is you want to express. This process may be called ‘subject analysis’, or ‘document analysis’, ‘content analysis’ or ‘concept analysis’. The subject content of items is sometimes also referred to more grandly as ‘intellectual content’ or ‘semantic content’, but these are simply other ways of defining what a document is about.

The problem of ‘aboutness’; indexer consistency and Subjectivity

The process of determining ‘aboutness’ is an essential part of subject cataloguing, but it contrasts markedly with the task of descriptive cataloguing. In the majority of cases the cataloguer has only to inspect the title page to determine the author and the title, and other bibliographic details of a book, and having found the author and title there is generally no dispute as to what they are. In some cases the subject is similarly straightforward, but in others the situation is more complicated. Unfortunately there is nowhere to look in a book which will tell you plainly and unequivocally what its subject is; you must decide this for yourself.