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