Uncertainty is the intrinsic property of spatial data and one of important factors affecting the course of spatial data mining. There are diversiform forms for the essentiality and aspect of uncertainty in the spatial objects of geographic information system. Essentiality of uncertainty may consist of the components of randomicity, fuzzy, chaos, etc. And the latter, i.e. aspect of uncertainty, may include error uncertainty, location uncertainty, attribute uncertainty, topology uncertainty, inconsonance uncertainty, immaturity uncertainty and so on. Spatial data mining, which is based on uncertainty, is the course of discovering knowledge in the spatial data including the attribute of uncertainty. Spatial data is the necessary object operated by spatial data mining and its uncertainty can exist in the whole process of data input, data processing, data output, etc. Uncertainty can affect directly or indirectly the quality of spatial data mining. Specially, uncertainty of spatial data ca...