Terms	Definitions
authority file	See subject authority file.
authority record	See subject authority record.
categorization scheme	See classification scheme.
classification scheme	The terms classification scheme, taxonomy, categorization scheme are often used interchangeably. Though there may be subtle differences from example to example, in general these types of KOSs provide ways to separate entities into buckets or relatively broad topic levels. Some examples provide a hierarchical arrangement of numeric or alphabetic notation to represent broad topics. These types of knowledge organization systems may not follow the strict rules for hierarchy required in the ANSI NISO Thesaurus Standard (Z39.19) (NISO), and often lack the explicit relationships presented in a thesaurus. [2]
concordance table	Also called a correspondence table. Methodologically, a concordance table describes the way in which terms in multiple vocabularies are related. [6]
cross-domain search	A search of multiple resources from different domains through a single interface, using a single query.
descriptors	Terms used in indexes, abstracts, or other databases/periodical indexes to describe the subjects of an article; sometimes called subject headings.
dictionary	Alphabetical lists of terms and their definitions that provide variant senses for each term, where applicable. They are more general in scope than a glossary. While a dictionary may also provide synonyms and through the definitions, related terms, there is no explicit hierarchical structure or attempt to group terms by concept. [2]
gazeteer	A dictionary of place names. Traditional gazetteers have been published as books or they appear as indexes to atlases. [2]
glossary	A list of terms, usually with definitions. The terms may be from a specific subject field or those used in a particular work. The terms are defined within that specific environment and rarely have variant meanings provided. Examples include the EPA Terms of the Environment. [2]
interoperability	The ability of two or more systems or components to exchange information and use the exchanged information without special effort on the part of either system. [1]
knowledge organization system	A general term referring to the tools that present the organized interpretation of knowledge structures; includes authority files, classification systems, concept spaces, dictionaries, gazetteers, glossaries, ontologies, subject heading sets, thesauri; often called KOS, sometimes, knowledge organization scheme. [2]
KOS	See knowledge organization system.
link	A mechanism for associating equivalent or associated terms.
map (verb)	To establish equivalence within a multilingual subject vocabulary; sometimes, term mapping or concept mapping; intellectual mapping refers to mapping done by persons, as opposed to machine-based mapping; machine-aided mapping combines machine and human effort.
networked knowledge organization system	An interactive information device aimed at supporting the description and retrieval of heterogeneous information resources on the internet; sometimes NKOS. [3]
NKOS	See networked knowledge organization system.
ontology	One example of a KOS. Ontologies are being developed as specific concept models by the Knowledge Management community. They can represent complex relationships between objects, and include the rules and axioms missing from semantic networks. Ontologies that describe knowledge in a specific area are often connected with systems for data mining and knowledge management. [2]
query term	The word or term with which a user begins a search.
semantic interoperability	The ability of two or more systems or components to exchange or harmonize cognate subject vocabularies and/or knowledge organization schemes to be used for the purpose of effective and efficient resource discovery without significant loss of lexical or connotative meaning and without special effort by the user
semantic network	A type of KOS that structures concepts and terms not as hierarchies but as a network or a web; concepts are thought of as nodes with various relationships branching out from them; the relationships generally go beyond the standard BT, NT and RT and may include specific whole-part relationships, cause-effect, parent-child, etc. Examples of semantic networks include Princeton’s WordNet, which is now used in a variety of search engines, and the Unified Medical Language System (UMLS) Semantic Network. [2]
subject authority file	An internal tool for catalog or database management. It contains authority records and provides documentation of a body or list of authorized and authoritative indexing terms in the context and framework of its vocabulary. [4]
subject authority record	A record of a subject heading that shows its established form, cites the authorities consulted in determining the choice and form of the heading, and indicates the cross-references made to and from the heading. [5]
subject headings	A set of controlled terms to represent the subjects of items in a collection. Subject heading lists can be extensive, covering a broad range of subjects. In use, subject headings tend to be pre-coordinated, with rules for how subject headings can be joined to provide more specific concepts. Examples include the Medical Subject Headings (MeSH) and the Library of Congress Subject Headings (LCSH). [2]
switching language	Intermediary terms that serve as a mechanism for moving between vocabularies; unlike links, which are internal, switching language is external to records for the terms being associated
taxonomy	See classification scheme.
term list	A list of words or phrases, often with definitions; examples include authority files, glossaries, gazetteers, and dictionaries [3]
thesaurus	A type of KOS, which is based on concepts that show relationships between terms. Relationships commonly expressed in a thesaurus include hierarchy, equivalence, and associative (or related). These relationships are generally represented by the notation BT (broader term), NT (narrower term), SY (synonym), and RT (associative or related). [2]
1	Report of the CC:DA Task Force on Metadata. http://www.libraries.psu.edu/tas/jca/ccda/tf-meta6.html
2	Gail Hodge, Systems of Knowledge Organization for Digital Libraries: Beyond Traditional Authority Files CLIR Pub91. April 2000. (www.clir.org/pubs/abstract/pub91abst.html); viewed at http://nkos.slis.kent.edu/KOS_taxonomy.htm
3	Zeng, Marcia Lei and Lois Mai Chan. Trends and issues in establishing interoperability among knowledge organization systems. JASIST, 55(5):377-395, 2004
4	Olson, Hope A., and John J. Boll. Subject analysis in online catalogs. Englewood, CO: Libraries Unlimited, 2001.
5	Chan, Lois Mai. Cataloging and classification: an introduction. 2nd ed. New York: McGraw-Hill, c1994.
6	UN glossary of classification terms. Online at http://unstats.un.org/unsd/class/family/glossary_short.htm. Accessed March 14, 2005.