Broad Path Decision in Vehicle System

This paper discusses how to decide a path for a vehicle to move to the destination. A space where vehicles move around is composed of space objects. The objects are structured in a hierarchical tree named a space tree. Objects at a higher level denote broader area than ones at a lower level in the space tree. In this paper, we present a method for each vehicle to decide a path whose part nearer to the vehicle is more detailed, and whose part which is farther from the vehicle is broader. A broader path means that it includes objects at higher level. Also, we model movement of the vehicle as an open nested transaction. Each vehicle locks objects in a decided path before passing through them at a level depending on the distance from the vehicle. The vehicle locks more strongly the object nearer to it. The strongness of the lock on the object represents how surely the vehicle can pass through the object. Also, we discuss the deadlock problem among multiple vehicles.