Similarity and Utility in Non-Numerical Domains

In complex situations that arise in the context of the design of large processes, the fault diagnosis of airplanes, or the organization of companies, one has to find good or best solutions although the problems are not clearly defined mathematically. Case-based reasoning (CBR) supports the use of recorded experience for such problem types. A central notion in CBR is similarity. We will discuss this notion by relating it to the concept of utility. At the same time we outline the building of CBR systems from this point of view. An example from software engineering will illustrate the approach. This is part of a much more complex enterprise in which both authors are involved from different point of views.