Transaction model of vehicle movement

This paper discusses a model of vehicle movement in a space tree where each object denotes a part of a path. Higher-level objects denote more abstract and broader paths than lower-level ones in the space tree. Vehicles first find broader paths which include higher-level objects in the space tree, and then the path is made more detailed as the vehicles are approaching the destinations. Movement of vehicle v on object o is atomic, i.e. v can either pass o or not. The atomic movement of v on o is decomposed into a sequence of atomic movements on the lower-level objects of o. Thus, the vehicle movement is modeled as a nested transaction which holds objects in the space tree. We discuss three schemes, i.e. close, semi-open, and open ones on when vehicles release the objects. We discuss how the releasing schemes can be adopted to the vehicle types and present the evaluation of the schemes