Abstract
End-user interactive access to complex information is one of the key functionalities of knowledge management systems. Traditionally, access paradigms have focused on retrieval of data on the basis of precise specifications: examples of this approach include queries on structured database systems, and information retrieval. However, most search tasks, and notably those typical of a knowledge worker, are exploratory and imprecise in essence: the user needs to explore the information base, find relationships among concepts, and thin alternatives out in a guided way.
Key Terms in this Chapter
Extensional Inference Rule: Two concepts A and B are related iff there is at least one item d in the knowledge base which is classified at the same time under A (or under one of A’s descendants) and under B (or under one of B’s descendants).
Taxonomy: A hierarchical organization of concepts going from the most general (topmost) to the most specific concepts. A taxonomy supports abstraction and models IS-A and/or PART-OF relations between a concept and its father. Tree taxonomies can be extended to support multiple inheritance (i.e., a concept having several fathers).
Taxonomy, Monodimensional: A taxonomy where an item can be classified under a single concept only.
Extension, shallow: Of a concept C, denotes the set of documents classified directly under C.
Extension, deep: Of a concept C, denotes the shallow extension of C union the deep extension of C’s sons.
User Focus: The set of documents corresponding to a user-defined composition of concepts; initially, the entire knowledge base.
Zoom: a user interface operation, that defines a new user focus by OR’ing user-selected concepts and AND’ing them with the previous focus; a reduced taxonomy is then computed and shown to the user.
Facet: One of several top level (most general) concepts in a multidimensional taxonomy. In general, facets are independent and define a set of “orthogonal” conceptual coordinates.
Taxonomy, multidimensional: A taxonomy where an item can be classified under several concepts.
Taxonomy, reduced: in a dynamic taxonomy, a taxonomy, describing the current user focus set F, which is derived from the original taxonomy by pruning from it all the concepts not related to F.
Subsumption: A subsumes B if the set denoted by B is a subset of the set denoted by A ( B ? A ).