ABSTRACT
The computer is a finite system. We cannot duplicate the infinite real world. Any representation stored in a geographical information system (GIS) is imperfect. The quality of the data within a GIS depends on several different components (e.g., inaccuracy, inconsistency and resolution). Consequently, any query result-generated by this GIS-introduces a level of uncertainty about the state of the quality of the outcome. It is important to provide the GIS user with the necessary awareness that these problems exist. Although there is a growing interest in improving data quality standards (CEN 1995, ISO 1998, SDTS 1994), commercial GIS packages put little or no effort in calculating and communicating the inherent imperfections to the user. In the literature (Chrisman 1983, Gopal 1989, Hunter and Beard 1992, Goodchild and Goodchild 1993, Heuvelink 1993, 1998, Guptill and Morrison 1995, Beard 1996, Parsons 1996), we can find several different approaches for handling either a single imperfection (e.g., inaccuracy) or a combination of imperfections (e.g., imprecision and inconsistency).
