首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 187 毫秒
1.
针对传统替换模型中缺乏事务支持而不可用的情况,提出了一种补偿支持的服务替换QoS模型.该模型充分考虑了服务间多关系以及事务Web服务特性,将事务补偿代价与替换选取代价有机结合,建立了全面评价补偿支持的替换服务QoS目标函数,在此基础上,提出了全新QoS驱动的补偿支持服务替换算法.实验证明该模型不仅保证了替换过程中事务原子性和数据一致性,而且提高了系统的可靠性和可信性.  相似文献   

2.
根据温控系统的特征以及需求说明,利用π-演算构建了该系统动态行为的交互模型,依据π-演算的反应规则仿真描述模型的行为交互过程,使用μ-演算和移动工作平台(MWB)工具分析和验证了该交互模型具有温度控制和阈值修改功能,从形式上证明了温控系统的需求说明及其π-演算模型的一致性。结果表明,π-演算能够清楚地描述和分析并发系统的行为交互,而μ-演算可以证明模型的有效性和正确性。  相似文献   

3.
针对物联网服务建模和验证问题,用π-演算理论对物联网服务和环境实体进行动态交互行为建模,并引入μ-演算刻画物联网服务能力,将其描述为物联网服务和环境实体动态交互行为的执行序列。针对特定的应用场景,使用π-演算定义了物联网服务和环境实体,利用μ-演算对物联网服务能力进行建模,使用检测工具MWB验证了模型的安全性、活性和时间约束三个性质,为物联网服务建模和验证提供了参考。  相似文献   

4.
针对现有语义Web服务组合方法未考虑到互联网环境的动态性及Web服务的随机性问题,提出采用流演算理论对语义Web服务组合进行研究.首先将Web服务的输入、输出、前提和效应映射为基于流演算的动作形式化描述; 然后定义将OWL-S中的原子过程和复合过程向流演算转换的规则; 再根据提供的Web服务组合目标,利用形式化地推理来得出Web服务的组合序列,从而能动态地形成正确有效的Web服务组合方案.最后,通过一个会议安排实例验证上述理论,结果表明该方法是可行的.  相似文献   

5.
面向服务工作流补偿机制的研究与实现   总被引:1,自引:0,他引:1  
为了解决面向服务工作流中异常的动态补偿问题,在传统工作流异常处理理论的基础上,结合Web Services的事务处理的特点,提出了基于工作流执行日志实施补偿的策略.补偿过程包括补偿判断、补偿路线产生和补偿行为调用,异常管理器控制补偿的执行过程.因为服务具有动态调用、动态执行特点,异常管理器需要在业务运行时依据工作流基本模式和事务依赖关系确定补偿范围,动态生成补偿路线并调用相应的补偿操作.为了验证补偿策略的可行性和正确性,实现了基于Web Services的原型系统WFCF.实验表明,该机制在失效补偿范围和补偿行为调用2个方面提高了工作流异常恢复的效率.  相似文献   

6.
验证问题是Web服务发展中亟待解决的关键问题之一,类型系统的加入以及Web服务动态的体系结构给问题的解决增添了很多难度。针对上述问题,在多元Pi-演算的基础上给出Web服务的描述模型和子类型关系定义,并对Web服务的相客性进行细化,给出Web服务可替换性定义;基于这些模型和定义,给出Web服务构造时类型正确性的判定规则和运行时可替换性的判定方法;最后用1个例子说明上述规则和方法的可行性结果表明上述模型、定义和方法为解决动态的、类型化的Web服务验证问题提供了理论依据和基础。  相似文献   

7.
通过使用交互服务集合的概念归纳出一个适用范围较广的Web服务可替换的充分条件,并基于Pi-演算对可替换条件中的兼容性条件进行建模,从Web服务可替换性和兼容性的关系入手,用求逆的方法证明了弱互模拟在语法兼容等条件下可保证服务兼容性和可替换性的结论.最后建立了一个关于投诉处理流程的实际模型,展示了如何应用Pi-演算的弱互模拟方法和形式化辅助工具对服务的可替换性进行判定.  相似文献   

8.
为了更全面地分析Web服务的失效过程,提高Web服务可靠性预测的精度,提出了一种Web服务可靠性的阶段模型.描述了SOA(service-oriented architecture)下Web服务在服务发布、服务发现、服务绑定、服务组合以及服务执行等各个阶段的失效过程,并根据Web服务在不同阶段的失效过程构建各个阶段的可靠性模型,将各阶段的可靠性模型集成起来即构成了Web服务的可靠性预测模型.通过实例描述了该模型的可靠性度量方法,并将该阶段模型和传统的可靠性模型进行了比较,实验结果表明了该可靠性阶段模型是有效的,因此比传统模型更加适用于Web服务.  相似文献   

9.
在回顾了目前关于面向服务以及面向Web服务的访问控制研究状况和进展的基础上,提出了一个全新的面向Web服务的动态分级角色访问控制模型.在该模型中,引入了授权组概念和分级访问控制机制,有效增强了Web服务访问控制的灵活性、独立性和扩展性,完善了Web服务权限管理,提高了Web服务应用的安全性,为Web服务提供了更为全面的访问控制机制.  相似文献   

10.
为了形式化地定义BPEL和BPEL4People的语义,提出了一个π演算的变种——πit演算。相对于传统的π演算,πit演算可以描述中断事件和时间事件,从而拥有更好的建模表达能力。介绍了πit演算的语法和语义,定义了一类强互模拟关系来判定πit演算进程间的行为等价,然后使用πit演算对BPEL和BPEL4People的活动进行了建模。该形式化模型有助于在BPEL和BPEL4People程序的设计阶段对其可靠性和一致性进行验证。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

13.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

14.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

18.
本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号