Principles underlying subject heading systems: what are they for?
As defined by the Working Group, its first aim is to facilitate subject access to information on an international level. This statement recognizes that subject information is difficult to pr ovide and to access beyond linguistic and other frontiers of the systems where it is generated. In order to improve communication in subject retrieval information, in addition to principles, practical devices at the level of real systems are needed. But since we start from an existing situati on where different systems appear with different backgrounds and features, we need to first establish the basis of a common understanding at the conceptual level. The expression of such conceptual common understanding may assist in developing SHLs by stating what is meant by a good SHL and what desirable construction and application principles are for such languages. This second purpose is a prospective one, assuming that existing standards and guidelines do not meet all the basic aspects that should be consid
