changing repositories. In faceted classification systems one does not have to know the name of the category into which an object is placed a priori. A controlled vocabulary is presented with the number of documents matching each vocabulary term. New facets may be created at any time without disruption of a single hierarchy or reorganizing other facets. Faceted classification systems make few assumptions about the scope and organization of the domain. It is difficult to break a faceted classification schema. See also Classification Research Group Controlled vocabulary Decimal classification Faceted search Findability Folksonomy Information architecture Tag (metadata) Universal Decimal Classification References External links How to Reuse a Faceted Classification and Put It On the Semantic Web Knowledge representation Library cataloging and classification