  To make an interactive guidance mechanism for document retrieval systems, we
developed a user-interface which presents users the visualized map of topics at
each stage of retrieval process. Topic words are automatically extracted by
frequency analysis and the strength of the relationships between topic words is
measured by their co-occurrence. A major factor affecting a user's impression
of a given topic word graph is the balance between common topic words and
specific topic words. By using frequency classes for topic word extraction, we
made it possible to select well-balanced set of topic words, and to adjust the
balance of common and specific topic words.
