Abstract : The diversity of spatial information systems promote the need to integrate heterogeneous spatial or geographic information systems (GIS) in a cooperative environment. We present an on going research project, called ISIS (Interoperable Spatial Information System), which aims to build an environment to support interoperability of GIS by interconnecting spatial data repositories and spatial processing resources. Our solution combines techniques from traditional interoperable information systems, spatial data modeling and distributed object oriented databases. While object oriented data modeling impact has been studied in spatial databases, research in model for distribution of both data and operations has received little attention. We focus on modeling problems and describe a hybrid spatial functional OO model that provides tools to model distribution and to resolve heterogeneities.