ABSTRACT
Geographic Information Systems are computer-based systems designed to support the capture, management, manipulation, analysis, modelling and display of spatially referenced data at different points in time (Aronoff, 1989). Today, GIS are widely used in many government, business and private activities, which fall into three major categories (Maguire et al., 1991):
1. socio-economic applications (for example, urban and regional planning, cadastral registration, archaeology, natural resources management, market analysis, etc.);
2. environmental applications (for example, forestry, fire and epidemic control, etc.); 3. management applications (for example, organization of pipeline networks and other services, such as
electricity and telephone, real-time navigation for vessels, planes and cars, etc.). The role of GIS in these applications is to provide the users and decision-makers with effective tools for solving the complex and usually ill-or semistructured spatial problems (Hopkins, 1984), while providing an adequate level of performance.
