VOCABULARIES FOR CO‐ORDINATE SYSTEMS

Indexing documents can be a purely mechanical operation or a highly intelligent one. It can be nothing more than a matter of listing the words in the title of the document, or it can be a detailed intellectual analysis of its content. But however the work is done, it ends up in the same way: the document gets labelled with a set of words (D). When it comes to searching the index, we again have to make up a set of words (Q). Retrieval is the operation of matching question words against document words. In co‐ordinate indexing, a document is retrieved if its word labels D include the question words Q. If we alter the words used for documents or questions, we affect the efficiency of the system.