When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for comp...When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster.展开更多
One way of achieving interoperability among heterogeneous, distributed DBMSs is through a multidatabase system. Recently, there is an increasing use of CORBA implementation in developing multidatabase systems. Panoram...One way of achieving interoperability among heterogeneous, distributed DBMSs is through a multidatabase system. Recently, there is an increasing use of CORBA implementation in developing multidatabase systems. Panorama is a multidatabase system that has been implemented on the top of CORBA compliant namely VisiBroker. It aims to achieve interoperability among Oracle, Sybase and other different DBMSs through the registration of these DBMSs to Panorama and through the single global query language PanoSQL designed for this system. In this paper, we first introduce CORBA for the interoperability in multidatabase systems. Then, a general view for our designed multidatabase system, Panorama, has been given. In section four, we introduce the global query language PanoSQL designed to achieve interoperability among the different DBMSs implemented in Panorama. Then, as an example, we present the registration of Oracle to Panorama in order to achieve interoperability in this system. And finally, a conclusion and the future work for this system have been given.展开更多
基金Project (No. 2004AA420100) supported by the National Hi-TechResearch and Development Program (863) of China
文摘When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster.
文摘One way of achieving interoperability among heterogeneous, distributed DBMSs is through a multidatabase system. Recently, there is an increasing use of CORBA implementation in developing multidatabase systems. Panorama is a multidatabase system that has been implemented on the top of CORBA compliant namely VisiBroker. It aims to achieve interoperability among Oracle, Sybase and other different DBMSs through the registration of these DBMSs to Panorama and through the single global query language PanoSQL designed for this system. In this paper, we first introduce CORBA for the interoperability in multidatabase systems. Then, a general view for our designed multidatabase system, Panorama, has been given. In section four, we introduce the global query language PanoSQL designed to achieve interoperability among the different DBMSs implemented in Panorama. Then, as an example, we present the registration of Oracle to Panorama in order to achieve interoperability in this system. And finally, a conclusion and the future work for this system have been given.
