The notion of KOS

In order to perform KO we need some schemes according to which subjects can be ordered. Any such scheme, whether simple or complex, is called a knowledge organization system.

This term is relatively recent, being connected with the increasing acknowledgment of KO as a unified field (see section 1.4.7). It has been spreading especially in the context of information representation and management on the world wide web, where a variety of conceptual tools are now described by this name. People thus discuss networked KOSs in a long-living series of workshops, and publish schemes in the SKOS format (see section 5.4).

In a similar way, the term controlled vocabulary (see section 3.2) is also used. Both a simple list of country names and a rich thesaurus can work as controlled vocabularies, stored in tables that can be related to other tables in the global data network; for example, the name of a product can be associated with the country where it is produced, and the label for the country will be taken from a controlled vocabulary of countries to ensure data consistency. However, the notion of KOS is broader than that of controlled vocabulary, as there are KOSs consisting of non-controlled labels, such as simple keywords.

Actually, schemes for organizing knowledge have existed since long before the term KOS appeared. Some decades ago they were often called indexing languages, as they usually consisted of words (or symbols working in a way similar to words) and worked according to morphological and syntactical rules that can also be found in the grammar of natural languages. Hutchins (1975) has a good discussion of the linguistic properties of KOSs.

Other terms that are often used to generically denote KOSs are classification (especially in a traditional or scientific context), taxonomy (especially in the context of website information architecture) and ontology (especially in computer science). Unfortunately, the term chosen depends more often on the cultural background of the author than on any differences in intended meanings. While all these terms may occasionally be meant as synonyms of KOS, they should properly denote different, specific KOS types. Therefore we will use them in their specific senses, which are discussed in detail in the following sections of this chapter.