Modelling Temporal Thematic Map Contents

Generally, the properties and the relations of geographic features are captured visually by maps. These maps are processed at one time and for one purpose. The time and purpose are set by a work demand and a need for decisions is based on available information. The class of maps that are developed to aid in decisions are called thematic maps. A thematic map is a map depicting selected kinds of information relating to one, or more specific themes, such as soil type, the incidence of a disease or land classification. In this paper, we will focus on temporal evolution of thematic maps in order to answer queries that refer to the time varying elements characterizing a thematic map, i.e., the geometric component of the map and the associated alphanumeric information. In this context, we first define through a {\it functional approach} (functional in the sense that it uses the function as mathematical structure) the notions of basic and thematic maps and a set of operators for the relative manipulation. Then, we define a space-time composite functional approach by associating time to the above mentioned notions in order to model the temporal evolution of maps information. In this context, we consider some new temporal operators. Finally, we illustrate the application of the proposed operators through some query examples.