As the volume of electronic information increases, there is growing interest in developing tools to help people better find, filter, and manage these resources. Text categorization - the assignment of natural language texts to one or more predefined categories based on their content - is an important component in many information organization and management tasks. Today, most text categorization is done by people.  Human categorization is very time-consuming and costly, thus limiting its applicability especially for large or rapidly changing collections. Consequently there is growing interest in developing technologies for (semi-)automatic text categorization. From the Series:CSE Colloquia - 1998