The ability to leverage organizational expertise is a critical success factor in most forms of knowledge work. However, expertise is an exceedingly difficult resource to manage. The design of computer-based support for knowledge management requires extensive, costly and inefficient cycles of knowledge elicitation to generate a reasonable knowledge map. We propose an alternative approximation technique which reduces these costs, while providing functionally equivalent data. In this methodological case study we chronicle the development of the key instrument in this approximation technique.