Abstract: Aiming at the applications of dynamic alliance and the business process re\|engineering of large enterprises, an agile workflow system is introduced in this paper, which supports system reconfiguration, software reusability, and scalable system. A workflow conceptual model based on process decomposition is given and some formal definitions describing this conceptual model are also presented.Based on this model,a multi\|layer architecture framework for this agile workflow system is designed.Two\|layers\|invoked function body encapsulation separately based on CORBA and agent enhances the software reusability and system reconfiguration capability. The multi\|layers architecture also enhances the system reconfiguration capability and the scalability.Key words workflow system, dynamic alliance, system reconfiguration, software reuse y, Wuhan 430062) (LIESMARS, Wuhan Technical University of Surveying and Mapping, Wuhan 430079) Abstract Collision with a fixed simple polygon Q may occur while a simple polygon P takes a rigid body displacement along regular curve σ . An optimal algorithm in worst case for collision test is given on O(mn) time, where m and n are sizes of P and Q . When P is a convex polygon, another practical algorithm for this collision test is designed by boundary combination operation of polygons and winding number with its algebraic properties.