Academic journal article Information Technology and Libraries

Graphical Table of Contents for Library Collections: The Application of Universal Decimal Classification Codes to Subject Maps

Academic journal article Information Technology and Libraries

Graphical Table of Contents for Library Collections: The Application of Universal Decimal Classification Codes to Subject Maps

Article excerpt

The representation of information content by graphical maps is an extended ongoing research topic. The objective of this article consists in verifying whether it is possible to create map displays using Universal Decimal Classification (UDC) codes (using co-classification analysis)for the purpose of creating a graphical table of contents for a library collection. The application of UDC codes was introduced to subject maps development using the following graphic representation methods: (1) multidimensional scaling; (2) cluster analysis; and (3) neural networks (self-organizing maps). Finally, the authors conclude that the different kinds of maps have slightly different degrees of viability and types of application.

Advanced techniques for information retrieval (IR) currently make up one of the most active areas of research in the field of library and information science. New models representing document content are replacing the classic systems in which search terms supplied by the user were compared against the indexing terms existing in the inverted files of a database. The objective of this article consists in verifying whether it is possible to create map displays using Universal Decimal Classification (UDC) codes, a classification system based on Dewey Decimal Classification, for the purpose of creating visualizations of a library collection.

One related topic of study in recent years is bibliographic browsing, a useful complement to querying strategies. Since the 1980s, a number of authors have dealt with this topic. For example, Ellis establishes that browsing is based on three different kinds of tasks: identification, familiarization, and differentiation. (1) Cove distinguishes three different browsing types: searching browsing, general purpose browsing, and serendipity browsing; whereas Bates presents six different types. (2) Yet most interesting is Bawden's browsing classification, which addresses similarity matching, structure-driven displays, and global vision. (3) Global-vision browsing implies the use of graphic representations, referred to in this article as map displays, that allow the user to grasp a global idea of the nature and structure of information in a database.

Several authors worked on this line of research throughout the 1990s, developing different types of maps. One of the most active authors was Lin, who introduced the concept of a graphical table of contents (GTOC) that is functionally analogous to the table of contents in the printed environment. (4) Lin applies the self-organizing map (SOM) algorithm to his own personal bibliography, analyzed by title and abstract fields, and represents it in a two-dimensional map. (5) The SOM algorithm is a major method for unsupervised learning, based on a grid of artificial neurons whose weights are adapted to match input vectors in a training set. It was first described by the Finnish professor Teuvo Kohonen and is thus sometimes referred to as a Kohonen map. (6) The algorithm takes a set of input objects, each represented by a vector in the matrix, and maps them onto nodes of a two-dimensional grid. Later on, Lin included such maps in the creation of GTOC Web sites based on a Java application.

Vectorization, the transformation of any information element into numerical data, using words from the title and abstract fields for co-word analysis, generates too large of a matrix, but this technique can be applied to reduced document sets. In this context, it is important to find some element that allows a less complex or "lighter" vectorization. Online public access library catalogs (OPACs) have certain elements, such as the subject codes of UDC, that can be more easily vectorized than free text in order to create GTOCs of a library collection.

Materials and methods

The OPAC selected for this study is that of the Public Library of Granada, which contains 32,700 records and 43,900 UDC codes, an average of 1. …

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