to record knowledge even if it is stored in non-conventional ways including materials in notebooks and ephemera. They also wanted their index to organize material systematically instead of alphabetically. The UDC has an overall taxonomy of knowledge that is extended with a number of facets, such as language, form, place and time. Each facet has its own symbol in the notation, such as: "=" for language; "-02" for materials, "[...]" for subordinate concepts. Faceted Classification for Occupational Safety and Health D. J. Foskett, a member of the Classification Research Group in London, developed classification of occupational safety and health materials for the library of the International Labour Organization. After a study of the literature in the field, he created the classification with the following facets: Facet A: Occupational Safety and Health: General Facet B: Special Classes of Workers, Industries Facet C: Sources of Hazards: Fire, Machinery, etc. Facet D: Industrial Accidents and Diseases Facet E: Preventive Measures, Protection Facet F: Organisation, Administration Notation was solely alphabetic, with the sub-facets organized hierarchically using extended codes, such as "g Industrial equipment and processes", "ge Machines". Art and Architecture Thesaurus (AAT) While not strictly a classification system, the AAT uses facets similar to those of Ranganathan's Colon Classification: Associated Concepts (e.g., philosophy) Physical Attributes Styles and Periods Agents (People/Organizations) Activities (similar to Ranganathan's Energy) Materials (similar to Ranganathan's Matter) Objects (similar to Ranganathan's Personality) Comparison between faceted and single hierarchical classification Hierarchical classification refers to the classification of objects using one single hierarchical taxonomy. Faceted classification may actually employ hierarchy in one or more of its facets, but allows for the use of more than one taxonomy to classify objects. Faceted classification systems allow the assignment of multiple classifications to an object, and enable those classifications to be applied by searchers in multiple ways, rather than in a single, predetermined order. Multiple facets may be used as a first step in a search process. For example, one may start from language or subject. Hierarchical classification systems are developed classes that are subdivided from the most general subjects to the most specific. Faceted classification systems allow for the combination of facets to filter the set of objects rapidly. In addition, the facets can be used to address multiple classification criteria. A faceted system focuses on the important, essential or persistent characteristics of content objects, helping it to be useful for categorization of fine-grained rapidly