摘要
随着计算机技术的发展,计算模式正逐步向“随时随地为人们提供服务”的普适计算过渡。随着网络技术和嵌入式技术的发展,各类便携、移动以及3C融合的产品逐渐融入并影响人们的日常生活,普适计算的基础设施逐渐成熟,以人为中心的普适服务成为发展的必然。如何保证保障普适服务质量是普适计算必须解决的一个关键环节,普适服务质量评价方法是普适计算研究的热点之一。
本文对服务质量评价技术进行了深入分析,并结合普适计算环境下的普适服务的特点开展了服务质量评价方法的研究,取得了以下研究成果。
1.系统地分析了现有的服务质量评价方法。目前的评价系统在一定程度上取得了一些成就,但是评价系统的客观性、扩展性、智能性和适应性不强,难以满足在普适环境下进行服务质量评价的技术要求。随着普适计算技术的发展,需要建立普适计算环境下的服务质量评价模型。
2.提出了局部模糊综合评价法。该方法采取不同的方式来处理评价系统的定性指标和定量指标,使评价更加客观。此外,采用分层结构,使得顶层指标屏蔽了不同服务质量评价标准的差异性。根据指标的性质不同,各层指标的权重赋值方式不同。各层指标在功能上相互联系,在管理和实现上相对独立,具有良好的可扩展性。
3.提出了基于用户信任度的延迟更新机制。针对现有的评价技术适应性弱、智能性不强等不足,提出了综合考虑用户信任度的更新机制。该算法考虑用户和系统的交互性,根据用户需求等外界环境变化形成的反馈信息和用户信任度,采用立即更新或者延迟更新的方式来修改当前的评价系统,同时,评估该反馈信息产生的反馈效果,以此调整用户的信任度。通过利用用户和系统的这种交互性,克服了评价系统一成不变的缺陷。仿真实验结果表明,该算法具有较好的收敛性和稳定性。
4.基于上述思想和架构,设计了一个合理的面向普适服务的服务质量评价模型。采用局部模糊综合评价法来建立评价模型,同时采用延迟更新机制进行评价模型的动态更新。将该模型系统应用到“健康普适服务评价系统”目标系统中,仿真结果表明,该模型是有效的。
Along with the development of computer techniques, the computing model is transmitting to pervasive computing which can serve people anytime and anywhere. With the development of network technology and embedded technology, various kinds of portable, mobile and 3Cs integration products gradually enter and effect human’s daily life. Infrastructure of pervasive computing is becoming mature and human-centered pervasive computing becomes an inevitable tendency in development.
To ensure the pervasive service quality is a key link which must be noticed and settled in pervasive computing. Pervasive service quality estimation method is one of the hotspots of pervasive computing research.
This thesis conducts analysis to estimation technology of quality of service in depth, and, combining features of pervasive service under pervasive computing environment, carries out research on service quality estimation method; then achieves as follows:
1. The thesis analyses the present service quality estimation method systematically. The current estimation system reaches some achievement but still is lack in objectivity, expansibility, intelligence, and suitability so that it is difficult to feed the technical requirements that develop service quality estimation under pervasion environment. With the development of pervasive computing technology, service quality estimation model needs to be established under the pervasive computing environment.
2. We put forward Local Fuzzy Comprehensive Estimation Method. This method processes quantitative and qualitative indexes of estimation system in different ways to make estimation more objective. Additionally, hierarchical structure makes top index shield emphasizes of different estimation standards of services qualities. According to their different characteristics, all layers of indexes, with flexibility and expansibility, connecting functionally, managing and realizing independently, have different weight assignment method.
3. We put forward delayed update mechanism based on users’trust level. On account of deficiency of flexibility, intelligence of estimation technique, the author advanced update mechanism comprehensively considering clients’trust level. The method modifies the present estimation system in the way of immediate or delayed updating according to the interactivity between users and system, as well as to users’trust level. Meanwhile it will adjust the users’trust level according to the feedback from users. The problem of system fixation is solved through the interactivity between clients and system. Result of simulation experiment shows that this computing method has the performance of convergence and robustness.
4. Based on the concept and framework mentioned above, the thesis design a reasonable quality-estimation model for pervasive service. This framework uses Local Fuzzy Comprehensive Estimation Method to establish estimation model, and delay update mechanism to conduct dynamic update of estimation model. The model system is used in target system of Healthcare Pervasive Service; the result of simulation experiment shows that the model is efficient.
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