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Introduction Since geographic information systems (GIS) currently dominate the perception of how computing and geography should interface, and since geocomputation is providing analysts of spatial phenomena with ever more powerful computing tools, it may be helpful to examine the experience that has accrued concerning links between them. Our examination is both empirical and normative, and the reader may find it useful to repeat at least some of our literature surveys, since new papers and articles are accumulating rapidly. Searching on the key words "GIS" and "model*" or "integrat*", where "*" is the wild card, led to a wide range of hits both in ISI Science and Social Science Citations Indices, and in OCLC-FirstSearch. These sources primarily contain journal articles, while conference proceedings may be searched at the Ohio State University GIS Master Bibliography Project, and more recently through the web-sites of conference organisers, such as NCGIA and GISDATA in Europe. Adding t

This paper provides a new representation for fields (continuous surfaces) in Geographical Information Systems (GIS), based on the notion of spatial functions and their combinations. Following Tomlin’s (1990) Map Algebra, the term “Map Calculus” is used for this new representation. In Map Calculus, GIS layers are stored as functions, and new layers can be created by combinations of other functions. This paper explains the principles of Map Calculus and demonstrates the creation of function-based layers and their supporting management mechanism. The proposal is based on Church’s (1941) Lambda Calculus and elements of functional computer languages (such as Lisp or Scheme).

This paper presents a conceptual Geographic Information System (GIS)-based site suitability analysis for a future water reclamation plant (WRP). The study area is situated in a portion of northern Los Angeles County that is currently experiencing one of the highest rates of population growth in Southern California. Potential sites for the WRP are evaluated utilizing a suitability index based on planning and design constraints, including parcel size, ground slope, land use, and distance to streams, residential areas, and biological resources. In order to minimize the inherent subjectivity of the selection process, the relative significance of each constraint is quantified by applying the Analytic Hierarchy Process (AHP) before determining the most suitable site.