Describing a teaching technique that promotes discovery. Thus, a heuristic model does not answer a question in and of itself, but rather helps create a means for answering a question. Phipps (1988) Geog. Anal. 20, 3 explains clearly, using as an example the search for a new house motivated by a housing problem. The searcher can make a rational inquiry to reduce this housing stress either by improving the old home, or by finding a new, less stress-inducing home, where cash is not a major issue. Or using a heuristic model, the searcher uses the information built up from each house visited to update his/her perceptions of the types of available houses within a price range. See N. Xiao in B. Warf (2010) on heuristic methods in spatial analysis.