地理位置路由协议被广泛应用于车载网络VANETs(vehicle Ad Hoc networks),然而在真实的城市场景中,由于复杂的道路拓扑和车辆移动,网络拓扑呈动态变化,给地理位置路由协议提出了挑战。传统的基于定向节点地理位置路由遭受可达性和可扩展性的折衷问题。为此,提出面向VANETs城市场景基于定向道路的地理位置路由ROGR(road-oriented geographic routing)协议。ROGR协议利用道路数字地图信息,并结合了基于源节点转发和基于接收节点转发机制。在每一跳中,利用数字地图信息和周期的beacon包,源节点计算各路段的权值;并选择具有最大权值的路段作为数据包传输路段,再将该路段上的车辆作为下一跳转发节点的候选节点。然后,这些候选节点利用基于退避时延机制竞争转发数据包。仿真结果表明,提出的ROGR协议具有好的可达性和可扩展性。
The extensions for logic-based knowledge bases with integrity constraints are rather popular. We put forward an alternative criteria for analysis of integrity constraints in Web ontology language （OWL） ontology under the closed world assumption. According to this criteria, grounded circumscription is applied to define integrity constraints in OWL ontology and the satisfaction of the integrity constraints by minimizing extensions of the predicates in integrity con- straints. According to the semantics of integrity constraints, we provide a modified tableau algorithm which is sound and complete for deciding the consistency of an extended ontol- ogy. Finally, the integrity constraint validation is converted into the corresponding consistency of the extended ontology. Comparing our approach with existing integrity constraint validation approaches, we show that the results of our approach are more in accordance with user requirements than other approaches in certain cases.
