MODELING THE NETWORK COMPONENT OF GEOGRAPHICAL INFORMATION-SYSTEMS

This paper presents a data model to manage networks with a Geographical Information System with some consideration of the path operator. The data model is based on the merge of graph theory concepts and the object-oriented paradigm. The introduction of the Master nodes (with respect to Master edges) allows definition of a node (with respect to an edge) as an abstraction of a sub-network. A network can be defined using several levels of definition (detail) following the importance of the nodes (with respect to the edges) within an application. The object-oriented concepts are applied to both the alphanumerical data part and to the modelling part of the topology of the graph. The data manipulation operators are basic operators. These operators are the union, an intersection and a difference. More elaborated operators, such as under constraints paths, are obtained by combining these basic operators. We present some considerations of the path operator in a GIS context and introduce the concept of the 'Open Graph Assumption' and the notion of direction. These notions take full advantage of the data model and represent an alternative way of defining the path operator. This modelling is well adapted to take account of multi-level networks (i.e., the definition of a view in the context of a multi-user configuration or cartographic generalization).