Geographic Information System(GIS) deal with data which can potentially be useful for a wida range of applications. However, the information needs of each application usually vary, specially in resolution, detail level, and representation style, as defined in the modeling phase of the geographic database design. To be able to deal with such diverse needs, the GIS must after features that allow multiple representations for each geographic entity of phenomenon. This paper addresses the problem of formal definition of the objects and their relationships on geographical information systems. The geographical data is divided in two main classes: geo-objects and geo-fields, which describe discrete and continuous representations of spatial reality. I will study the classes and the roles of relationships over geo-fields, geo-objects and nongeo-objects. Therefore, this paper will contribute the efficient design of geographical class hierarchy schema by means of formalizing attribute-domains of classes.