ABSTRACT
In the library and information sciences, classification theories are used primarily for knowledge organization, either in a manual or in a machine environment. In this context, classification theories have usually been developed initially as a support for specific knowledge organization classification systems, although the theories and the systems have influenced and re-influenced each other in particular ways throughout their lives. This entry discusses theories for knowledge organization classifications using examples from a number of classification systems, but no one system is discussed at length. Instead, the entry is organized into sections that deal first with classificatory issues in general and then with theories of content, theories of structure, and theories of notation for knowledge organization classifications.
