"For example, suppose the concept air-to ground missile was a part of our knowledge scheme, but not ground-to air missile. In an enumerated scheme, a category would exist:
but not the other term. A book on ground-to-air missiles would have to be classified under a more general term, such as "Weapons."
In a facet scheme these terms would exist:
and this would allow us to easity fit together each type of classification:
What follows is a brief description of Ranganathan's classification theory.
"The Colon Classification system, like enumerative classification systems, divides the universe of knowledge into a number of main classes, such as agriculture, philosophy, and literature. Dewey Decimal Classification, for example, has ten main classes, labeled zero through nine. The Colon Classification system has 42 main classes, labeled with one or two letters of the alphabet. A few are labeled with number or Greek letters. But Colon Classification, rather than simply dividing the main classes into a series of subordinate classes, as most systems do, subdivides each main class by particular characteristics into facets. The facets, which are labeled in the Colon Classification system by Arabic numbers, are then combined to make subordinate classes as needed. For example, literature may be divided by the characteristic "language" into the facet of language, including English, German, and French. It may also be divided by "form" which yeilds the facet of form, including poetry, drama, and fiction.
Colon Classification contains both basic subjects and their facets, which contain isolates. A basic subject can stand alone, for example, "literature" in the subject "English literature". An isolate, in contrast, is a term that mediates a basic subject, such as the term "English." To create a class number, the basic subject is named first. The isolates follow, entered according to a facet formula. This formula states that every isolate in every facet is a manifestation of one of five fundamental categories, personality, matter, energy, space, and time. Personality is the distinguishing characteristic of a subject. Matter is the physical material of which a subject may be composed. Energy is any action that occurs with respect to the subject. Space is the geographic component of the location of a subject. And time is the period associated with a subject.
Thus, the basic subject "handicrafts" of the topic "19th-century woven wool Peruvian clothing handicrafts" would have the isolate from the personality facet "clothing"; from the matter facet, "wool"; from the energy facet, "woven"; from the space facet, "Peru"; and from the time facet, "19th century". Some topics have fewer than five fundamental categories. And some have more than one facet in a given fundamental category. Isolates are always arranged in order of decreasing concreteness, based on the fundamental categories. Personality is considered the most concrete and time the least concrete. The acronym PMEST helps the classifier remember the formula and its order."*
Cleveland, Donald B. and Cleveland, Ana D.Introduction to Indexing and Abstracting. Englewood, Colorado : Libraries, Unlimited, 1990.
Current Contents, #7, p.3-7, February 13, 1984; http://126.96.36.199/eugene_garfield/volume7.html
last updated on 09/20/99