ABSTRACT
The Socio-Economic Units (SEUs) are deeply related to the real situation of the ground and to the land use classification and definition. According to Clawson and Stewart the classification should be based on what the observer sees on the ground so that his personal interpretation plays a marginal role (Clawson and Stewart, 1965; Stewart, 1959). As far as the information data is concerned, the area on the ground should be “the smallest recognizable and geographically identifiable parcel or tract of land”. Of course, these are ideal characteristics. In general the classification and the geographic encoding are related to the decisions taken by survey and planning authorities, and therefore they are strongly related to the data collected in the past and to the way they were collected. As planning process needs time to develop and in its successive steps is producing new data, the compatibility with the old ones has to be taken seriously into consideration. The compatibility is based on the spatial definition of elementary units, on the type of data collected, and on the time they were collected. Time compatibility is easily provided by the frequency of data collecting. Type of data and spatial definition should be submodules of older data so as to allow historical database comparative analysis.
