Representation and reasoning with qualitative spatial relations is an important problem in artificial intelligence and has wide applications in the fields of geographic information system, computer vision, autonomous robot navigation, natural language understanding, and spatial databases etc. The reasons for this interest in using qualitative spatial relations include cognitive comprehensibility, efficiency and computational facility. This paper summarizes progress in qualitative spatial representation by describing key calculi representing different types of spatial relationships. The paper concludes with a discussion of current research and glimpse of future work.

Abstract-Vehicular ad hoc networks (VANETs) are emerging as a new network environment for intelligent transportation systems (ITS). In many applications envisaged for VANETs, traffic information needs to be disseminated to a group of relevant vehicles and maintained for a duration of time. Here a system of abiding geocast is presented for disseminating warning message among mobile vehicles in VANETs. In this system vehicles on a stretch of roads carry safety messages to vehicles in the opposite direction, so as to warn them regarding a dangerous situation ahead. The objective is that as much as possible all relevant vehicles receive the warning before they reach the warning line, whereas as few messages are broadcasted as possible. Opposite vehicles are preferred as relays to reduce broadcast overhead and help message delivery upstream. Furthermore, wait time of individual relay vehicles are set dynamically for the next broadcast, thus unnecessary broadcasts can be saved while keeping the warning message in the affected area. Simulations show the quality of the proposed system by measuring the broadcast overhead under various conditions.

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