This paper describes a document retrieval system called CAIRN that uses a c
ase-based reasoning set using a large lexicon to automatically generate a c
ase index to that document set. The index is used by a case-based retrieval
engine to find documents. The retrieval engine is tolerant of noisy natura
l language queries. CAIRN also supports failure-driven learning of importan
t concepts during its use and thus can significantly improve its retrieval
accuracy over time. The limitations of this system are discussed. (C) 1998
Elsevier Science B.V. All rights reserved.