An affinity relationship index and a method for using it are disclosed. The affinity relationship index captures, for any given place name, an affinity to one or more potentially more important place names. Each such more important place subtends an affinity domain within which other places are deemed to lie. The index carries this on hierarchically and has the effect of creating a relatively meaningful and minimized structure that can be rapidly searched for a user's intended destination. An application uses these affinity domains to determine the instructions necessary to embark upon a guided journey rather than determining all instructions needed to complete the journey.