审计系统作为安全信息系统的一个重要组成部分,对于监督系统的正常运行、保障安全策略的正确实施、构造计算机入侵检测系统等都具有十分重要的意义。审计缓冲区的管理是审计系统的核心部分,本文利用时序 Petri 网对审计缓冲区管理的实现方案进行建模,进而对系统的安全性和活性进行了分析和验证。该方法利用时序逻辑扩充了 Petri 网缺乏描述系统事件之间时序关系的局限性,同时发挥了 Petri 网对系统并发和物理结构的有效描述及分析的优势,达到了系统验证的目的。
本文给出了网格计算资源的三层调度方案,并利用层次颜色 Petri 网对这一调度方案进行了建模与分析。对不同层次的资源调度建立了相应的颜色时延 Petri 网模型,不同层次的颜色时延 Petri 网模型可以有不同的行为表现,体现了网格计算资源的异构、自治等特点。给出了层次颜色 Petri 网的可达任务图的概念及构造算法,并利用可达任务图,对网格计算资源调度系统的运行状态进行了分析。
Efficient task scheduling is critical to achieving high performance on grid computing environment. The task scheduling on grid is studied as optimization problem in this paper. A heuristic task scheduling algorithm satisfying resources load balancing on grid environment is presented. The algorithm schedules tasks by employing mean load based on task predictive execution time as heuristic information to obtain an initial scheduling strategy. Then an optimal scheduling strategy is achieved by selecting two machines satisfying condition to change their loads via reassigning their tasks under the heuristic of their mean load. Methods of selecting machines and tasks are given in this paper to increase the throughput of the system and reduce the total waiting time. The efficiency of the algorithm is analyzed and the performance of the proposed algorithm is evaluated via extensive simulation experiments. Experimental results show that the heuristic algorithm performs significantly to ensure high load balancing and achieve an optimal scheduling strategy almost all the time. Furthermore, results show that our algorithm is high efficient in terms of time complexity.
