Visual Summaries of Geographic Databases Visual Summaries of Geographic Databases by Chorems

Traditional cartography is a fundamental tool to visually describe facts and relationships concerning with territory. This is a well-known and well-established approach and decision makers are usually satisfied by its expressiveness when it concerns the cartography of facts. Differently, this kind of cartography may fail when dealing with scenarios referring to heterogeneous issues, such as political, economic and demographic problems, due to the large amount of complex data to represent in a map. Then, more effective solutions in supporting users to locate facts, trends and new patterns should be investigated. In this dissertation the research carried out within an international project is presented, meant to define cartographic solutions able to better represent geographic information extracted from database contents, which refer both to geographic objects and spatio-temporal phenomena. An actual support for human activity to model and analyze the reality of interest may indeed consist of an immediate synthesis of the most relevant data, disregarding details. Such a synthesis may be based on the usage of visual metaphors, which are able to capture and restitute the most salient features of a scenario. Moreover, it may represent the starting point for further processing tasks aimed to derive spatial analysis data, and to support expert users in decision making, thus bridging the gap between the complexity of the adopted applications and the need for rapid and exhaustive responses expected by domain experts. The major contribution of this work along this line has been to define a methodology to visualize geographic database summaries, expressing them through “schematized representations of territories”, known as chorems. In particular, two specific contributions have been produced by investigating and implementing the proposed methodology. The former consists of the formal specification of chorems in terms of visual language and structure, in order to both standardize the chorem creation and assembling process and provide a usable framework for computer systems. The latter is represented by the design and the implementation of a system which generates maps containing chorems starting from geographic database content, in a semi-automatic manner.