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81.
针对现有用户-用户的角色转授权模型存在授权冲突问题,基于转授权的组件、相关性质以及约束规则,提出了一种约束转授权模型,该模型满足最小特权和职责分离两安全原则,给出了该模型的体系架构和功能描述;以此模型为背景介绍了一种约束描述语言及其形式化语义描述;通过规约算法和构造算法论证了它与严格形式上的一阶谓词逻辑是等价的,并对该约束语言的合理性和完整性进行了讨论;最后用该约束语言给出了模型的表现能力,较好的解决了转授权冲突问题。 相似文献
82.
本文针对具有严格时间要求的系统,阐述并分析了三种利用实时逻辑实现时间约束检测的方法。第一种方法通过检测系统规范和安全性断言的一致性来验证约束的满足性,非常适合于系统规范的设计与可满足性检测,算法的时间复杂度是O(n^2) O(n^2) O(2^k)。第二种方法利用实时逻辑与约束图的方法实现运行时的时间约束检测,但检测时的系统约束条件不够第三种方法简约,算法时间复杂度为O(n^2),改进之后为O(n^2)。第三种方法通过对约束图的处理,减少运行时系统检测的约束条件,从而减少运行时的时间约束条件的搜索时间,算法的时间复杂度为O(n),在实时性和检测效率明显优于前两种方法。但需要运行前优化约束规则,将会增加额外的时间和空间复杂度。 相似文献
83.
We study the isomorphic implication problem for Boolean constraints. We show that this is a natural analog of the subgraph
isomorphism problem. We prove that, depending on the set of constraints, this problem is in P, or is NP-complete, or is NP-hard,
coNP-hard, and in P‖NP. We show how to extend the NP-hardness and coNP-hardness to P‖NP-hardness for some cases, and conjecture that this can be done in all cases.
Supported in part by grants NSF-CCR-0311021 and DFG VO 630/5-1 and VO 630/5-2. An extended abstract of this paper appears
in Proceedings of the 30th International Symposium on Mathematical Foundations of Computer Science (MFCS 2005), pp. 119–130, Springer-Verlag Lecture Notes in Computer Science #3618, August 2005.
Work of M. Bauland done in part while visiting CASCI’s Laboratory for Complexity at Rochester Institute of Technology.
Work of E. Hemaspaandra done in part while on sabbatical at the University of Rochester. 相似文献
84.
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86.
Construction requirements represent the key preconditions for construction. These include topological precedence, key resources, space requirements, etc. Consequently, identifying them is necessary for feasible construction planning to be achieved. Despite this, little attention has been given to the impact of construction requirements on a project schedule, possibly because of the lack of a good tool for representing these requirements. This paper distinguishes construction requirements into static and dynamic types, according to changes in the need of the requirement during its life cycle. A modeling framework, PDM++, is then proposed. The framework deals with schedule constraints arising from both static and dynamic construction requirements, provides greater semantic expression to capture schedule constraints unambiguously, and facilitates the representation of interdependent conditional relationships. The concept of meta-intervals is also devised to represent complex requirements involving several activities and schedule constraints, and it facilitates modeling at higher levels of plan abstractions. Finally, an illustrative case study is presented to show the applicability of PDM++ in representing schedule constraints and alternative scheduling from a construction requirements perspective. 相似文献
87.
Building on the Theory of Constraints (TOC) in the service context and drawing on internal and external service profit chain literature, we explore the role of throughput orientation at the manager-employee-customer triad level. Controlling for archival performance data at the branch level of banks, in a sample of 136 triads of managers-frontline employees-customers at 37 branches from a bank in a northern state in India, we find that throughput orientation is positively associated with external service profit chain; and this association is further strengthened under stronger internal service profit chain. By integrating a service-operations based perspective of service employees at a triadic level, we demonstrate the importance of throughput orientation in service profit chains. 相似文献
88.
Darius Grabowski Daniel Platte Lars Hedrich Erich Barke 《Electronic Notes in Theoretical Computer Science》2006,153(3):37
In this contribution we present algorithms for model checking of analog circuits enabling the specification of time constraints. Furthermore, a methodology for defining time-based specifications is introduced. An already known method for model checking of integrated analog circuits has been extended to take into account time constraints. The method will be presented using three industrial circuits. The results of model checking will be compared to verification by simulation. 相似文献
89.
This paper begins by examining the ‘classical’ raster-based composition model, establishing its weakness, and developing a new composition algebra based on line drawing. It then examines the role of composition in the Hierarchical Display Model, demonstrates that the forms of composition assumed in this model are inadequate to deal correctly with the interactions of two-dimensional representations of three-dimensional objects, and shows that our composition algebra resolves this difficulty. The composition steps required can be packaged with the use of a single attribute which constrains the apparent order of composition. This attribute is associated with the object which is to be taken ‘out of order’, obviating any needsfor layers. 相似文献
90.
We present an O(n3) time type inference algorithm for a type system with a largest type, a smallest type , and the usual ordering between function types. The algorithm infers type annotations of least shape, and it works equally well for recursive types. For the problem of typability, our algorithm is simpler than the one of Kozen, Palsberg, and Schwartzbach for type inferencewithout . This may be surprising, especially because the system with is strictly more powerful. 相似文献