  This paper describe a methodology for semi-automatic classification schema
definition (a classification schema is a taxonomy of categories useful for
automatic document classification). The methodology is based on: (i) an
extensional approach useful to create a typology starting from a document base,
and (ii) an intensional approach to build the classification schema starting
from the typology. The extensional approach uses clustering techniques to group
together documents on the basis of a similarity measure, whereas the
intensional approach uses different operations (aggregation, reduction,
generalization specialization) to define classes. keywords: ontology,
classification schema, fundamentum divisionis, cluster analysis classification
task.
