The delegation-agent models in agricultural insurance are established both under the circumstances of information symmetry and information asymmetry.Insurers choose effort level-a* according to the first order optimal...The delegation-agent models in agricultural insurance are established both under the circumstances of information symmetry and information asymmetry.Insurers choose effort level-a* according to the first order optimal condition of ∫{v(π-s(π))+λ11[u(s(π))]fa(π,a*)}dπ=λ11c'(a*)u(s(π)) at the present stage when the information is symmetric.While the information is asymmetric,the first order optimal condition changed into v'(π-s(π))u'(s(π))=λ21+μ21(1-fa(π,a)f(π,a)).In other words,the higher the output,the more and more income of insured.The paper also modifies the models,when the information is symmetric,the insurers determine the effort level of insured-a* based on the first order optimal condition of ∫{v(π-s(π))+λ12[u(s(π))]fa(π,a*)}dπ=λ12h'(a*)u(s(π));to the contrary,the first order optimal condition would change into v'(π*-s(π*))u'(s(π*))=λ22+μ22(1-fa(π,a)f(π,a))-λh(a)f(π,a)-μh'(a)f(π,a).The results show that the insured and the insurers would both benefit from the insurance when the effort cost function related to the expectation of the insured(agricultural producers).If the insured manage the objects of insurance more seriously,the rate of disasters would be lowered.Therefore,the insurance claimed against the insured would be lessened,and the benefits of the insurers would be increased at last.展开更多
New challenges are introduced when people try to build a general-purpose mobile agent middleware in Grid envi- ronment. In this paper, an instance-oriented security mechanism is proposed to deal with possible security...New challenges are introduced when people try to build a general-purpose mobile agent middleware in Grid envi- ronment. In this paper, an instance-oriented security mechanism is proposed to deal with possible security threats in such mobile agent systems. The current security support in Grid Security Infrastructure (GSI) requires the users to delegate their privileges to certain hosts. This host-oriented solution is insecure and inflexible towards mobile agent applications because it cannot prevent delegation abuse and control well the diffusion of damage. Our proposed solution introduces security instance, which is an en- capsulation of one set of authorizations and their validity specifications with respect to the agent’s specific code segments, or even the states and requests. Applications can establish and configure their security framework flexibly on the same platform, through defining instances and operations according to their own logic. Mechanisms are provided to allow users delegating their identity to these instances instead of certain hosts. By adopting this instance-oriented security mechanism, a Grid-based general-purpose MA middleware, Everest, is developed to enhance Globus Toolkit’s security support for mobile agent applications.展开更多
A new event-handling paradigm and its application model are proposed. The working mechanism and principle of event listener model is given in detail. Finally, the launching event mechanisms, the choosing event handlin...A new event-handling paradigm and its application model are proposed. The working mechanism and principle of event listener model is given in detail. Finally, the launching event mechanisms, the choosing event handling models and the dispatching mechanism are illustrated.展开更多
针对现有RBAC(Role-Based Access Control)委托授权模型存在的不足:其一,没有有效地实现细致委托粒度;其二,权限传播没有得到很好的控制,给出一种基于映射机制的细粒度角色委托模型RDBMPM(Fine-Grained Role Delegation Model Based Per...针对现有RBAC(Role-Based Access Control)委托授权模型存在的不足:其一,没有有效地实现细致委托粒度;其二,权限传播没有得到很好的控制,给出一种基于映射机制的细粒度角色委托模型RDBMPM(Fine-Grained Role Delegation Model Based Permission Mapping Mechanism),该模型基于向量化与度量化算子的复合运算,提出了度量角色的概念,并以其为授权粒度对委托约束机制进行讨论,增强了权限传播的可控性.最后,通过三个典型的支持细粒度委托的模型在映射机制下的具体实现,验证了RDBMPM模型的研究意义.展开更多
PMI是构建在PKI基础上实施特权管理的服务体系,目前普遍采用基于角色的安全架构和基于属性证书的实现机制。该文提出了一种面向PMI环境基于角色和权限两级的开放分布式委托授权模型――DM for PMI(Delegation Model for PMI),并在该模...PMI是构建在PKI基础上实施特权管理的服务体系,目前普遍采用基于角色的安全架构和基于属性证书的实现机制。该文提出了一种面向PMI环境基于角色和权限两级的开放分布式委托授权模型――DM for PMI(Delegation Model for PMI),并在该模型的基础上引入委托证书,给出了一种扩展的PMI体系架构――EPMI(Extension PMI)。EPMI增强了原有PMI中委托授权的语义和机制,解决了开放分布式环境下电子政务与电子商务实际应用中的特权委托问题。展开更多
文摘The delegation-agent models in agricultural insurance are established both under the circumstances of information symmetry and information asymmetry.Insurers choose effort level-a* according to the first order optimal condition of ∫{v(π-s(π))+λ11[u(s(π))]fa(π,a*)}dπ=λ11c'(a*)u(s(π)) at the present stage when the information is symmetric.While the information is asymmetric,the first order optimal condition changed into v'(π-s(π))u'(s(π))=λ21+μ21(1-fa(π,a)f(π,a)).In other words,the higher the output,the more and more income of insured.The paper also modifies the models,when the information is symmetric,the insurers determine the effort level of insured-a* based on the first order optimal condition of ∫{v(π-s(π))+λ12[u(s(π))]fa(π,a*)}dπ=λ12h'(a*)u(s(π));to the contrary,the first order optimal condition would change into v'(π*-s(π*))u'(s(π*))=λ22+μ22(1-fa(π,a)f(π,a))-λh(a)f(π,a)-μh'(a)f(π,a).The results show that the insured and the insurers would both benefit from the insurance when the effort cost function related to the expectation of the insured(agricultural producers).If the insured manage the objects of insurance more seriously,the rate of disasters would be lowered.Therefore,the insurance claimed against the insured would be lessened,and the benefits of the insurers would be increased at last.
基金Project (No. 602032) supported by the Natural Science Foundationof Zhejiang Province, China
文摘New challenges are introduced when people try to build a general-purpose mobile agent middleware in Grid envi- ronment. In this paper, an instance-oriented security mechanism is proposed to deal with possible security threats in such mobile agent systems. The current security support in Grid Security Infrastructure (GSI) requires the users to delegate their privileges to certain hosts. This host-oriented solution is insecure and inflexible towards mobile agent applications because it cannot prevent delegation abuse and control well the diffusion of damage. Our proposed solution introduces security instance, which is an en- capsulation of one set of authorizations and their validity specifications with respect to the agent’s specific code segments, or even the states and requests. Applications can establish and configure their security framework flexibly on the same platform, through defining instances and operations according to their own logic. Mechanisms are provided to allow users delegating their identity to these instances instead of certain hosts. By adopting this instance-oriented security mechanism, a Grid-based general-purpose MA middleware, Everest, is developed to enhance Globus Toolkit’s security support for mobile agent applications.
文摘A new event-handling paradigm and its application model are proposed. The working mechanism and principle of event listener model is given in detail. Finally, the launching event mechanisms, the choosing event handling models and the dispatching mechanism are illustrated.
基金the National Natural Science Foundation of China under Grant No.60603017 (国家自然科学基金)the National High-Tech Research and Development Plan of China under Grant No.2006AA01Z454 (国家高技术研究发展计划(863))the National Key Technology R&D Program of China under Grant No.2006BAH02A02 (国家科技支撑计划)
文摘针对现有RBAC(Role-Based Access Control)委托授权模型存在的不足:其一,没有有效地实现细致委托粒度;其二,权限传播没有得到很好的控制,给出一种基于映射机制的细粒度角色委托模型RDBMPM(Fine-Grained Role Delegation Model Based Permission Mapping Mechanism),该模型基于向量化与度量化算子的复合运算,提出了度量角色的概念,并以其为授权粒度对委托约束机制进行讨论,增强了权限传播的可控性.最后,通过三个典型的支持细粒度委托的模型在映射机制下的具体实现,验证了RDBMPM模型的研究意义.
文摘PMI是构建在PKI基础上实施特权管理的服务体系,目前普遍采用基于角色的安全架构和基于属性证书的实现机制。该文提出了一种面向PMI环境基于角色和权限两级的开放分布式委托授权模型――DM for PMI(Delegation Model for PMI),并在该模型的基础上引入委托证书,给出了一种扩展的PMI体系架构――EPMI(Extension PMI)。EPMI增强了原有PMI中委托授权的语义和机制,解决了开放分布式环境下电子政务与电子商务实际应用中的特权委托问题。
