This paper presents a refinement calculus for service components. We model the behaviour of individual service by a guarded design, which enables one to separate the responsibility of clients from the commitment made by the system, and to identify a component by a set of failures and divergences. Protocols are introduced to coordinate the interactions between a component with the external environment. We adopt the notion of process refinement to formalize the substitutivity of components, and provide a complete proof method based on the notion of simulations.
利用结构分析与设计语言AADL(Architecture Analysis and Design Language)对无线传感器网络进行建模,并对其中一个节点进行了详细的分析。介绍AADL语言以及它在嵌入式系统中建模的优势,展示了无线传感器网络的特征和关键技术。结合AADL,针对温度传感器案例,对温度传感器的结构及功能进行了详细描述,充分体现了此传感器节点的工作原理与内部结构,有助于提高其结构上的可改进性和扩展性,以进一步应用到传感器网络中。
Most effcient indeces and query techniques over XML(extensible markup language) data are based on a certain labeling scheme,which can quickly determine ancestor-descendant and parent-child relationship between two nodes.The current basic labeling schemes such as containment scheme and prefix scheme cannot avoid relabeling when XML documents are updated.After analyzing the essence of existing dynamic XML labels such as compact dynamic binary string(CDBS) and vector encoding,this paper gives a common unifying framework for the numeric-based generalized dynamic label,which can be implemented into a variety of dynamic labels according to the different user-defined value comparison methods.This paper also proposes a novel dynamic labeling scheme called radical sign label.Extensive experiments show that the radical sign label performs well for the initialization,insertion and query operations,and especially for skewed insertion where the storage cost of the radical sign label is better than that of former methods.
