So very many people have touched my life over the course of this odyssey. For those that may escape mention here|a dissertation in itself|I have made the last to be rst, and I perhaps owe you a drink.Resounding thanks and a c horus of gratitude to my advisor, David Leake, for all of his support, guidance, and encouragement. David has always been available with a cheerful word, whether dispensing encyclopedic knowledge about relevant people and research, providing constructive criticism, wrestling with the deep and fundamental mysteries of CBR, or simply chatting away. He has done his best to keep me out of trouble for the better part of a decade.I also want to thank the members of my committee, Mike Gasser, Randy Bramley, and Dirk Van Gucht. I very much appreciate their perspective, assistance, advice, and support.I would like to thank the host of Arti cial Intelligence, Cognitive Science, and especially CRANIUM lab members for their helpful ideas, for their support and wisdom, and for the use of their books. They made the lab a comfortable home away from home. Lab members have included: