ABSTRACT
English literature German literature French literature Poetry Drama Fiction Poetry Drama Fiction Poetry Drama Fiction Thus each entity (for example English poetry) falls into a subgroup of a larger group (for example English literature), which in turn forms part of an even larger group (for example Literature). Such a classification is built up by a process of division, according to certain characteristics. Literature can be divided into sub-classes by the characteristic of language, that is English literature, German literature, French literature. Each of these classes can then be further subdivided by the characteristic of form of literature, that is, English poetry, English drama, English fiction; German poetry, German drama, German fiction, and so on. This is sometimes referred to as a ‘top down’ approach (as compared with that of a faceted system which utilises a ‘base-up’ technique). The tree structure shown above could be presented thus:
Literature
English literature Poetry Drama Fiction
German literature Poetry Drama Fiction
French literature Poetry Drama Fiction
This is near to the way in which the classification schedules would be written down or printed. As the process of division continues, the hierarchical classification lists or ‘enumerates’ (hence ‘enumerative’ classification) complex subjects, for example ‘English poetry’, which comprises a language (English) and a literary form (poetry). This may be contrasted with the faceted approach, which would list ‘English’ and ‘poetry’ as separate concepts but not as a complete subject. In a properly designed hierarchical classification each subject should have only one place where it fits into the system. Order in array In a hierarchical scheme the order of subjects at a particular level of division is important. This order corresponds to the order of concepts within facets and should be as helpful to the user as possible. For example, in literature, at the language level it might be helpful to place the ‘home’ language, for example English, first, then related European languages followed by other languages. Citation order The citation order in a hierarchical classification is derived from the order in which the characteristics of division are applied. In the literature example, above, the first characteristic of division is language and the second literary form. The citation order is therefore: Language → Form but this citation order is ‘in-built’ to classification numbers for complex subjects listed in the scheme. Notation Here is the above scheme with a simple notation consisting of numeric digits added:
1 Literature 11 English literature 111 Poetry 112 Drama 113 Fiction
12 German literature 121 Poetry 122 Drama 123 Fiction 13 French literature 131 Poetry 132 Drama 133 Fiction
This notation may be described as: Pure Only one type of symbol is used (the numeric
digit). Expressive It reflects the structure of the classification; 111
‘English poetry’ is a division of 11 ‘English literature’, which in turn is a division of 1 ‘Literature’.
