Synchronization Algebras with Mobility for Graph Transformations

We propose a generalization of synchronization algebras that allows to deal with mobility and local resource handling. We show how it can be used to model communication primitives for distributed and mobile computations, such as the ones used in the global computing area. We propose a graph transformation formalism in the Synchronized Hyperedge Replacement approach which is parametric w.r.t. the synchronization algebra and thus allows to model complex systems based on the chosen communication primitives. We thus unify different models described in the literature and we allow to easily define new ones. We present various examples and a case study on Fusion Calculus, showing how different semantics for it can be derived using different synchronization algebras.     

Towards Behavioral Maude: Behavioral Membership Equational Logic

How can algebraic and coalgebraic specifications be integrated? How can behavioral equivalence be addressed in an algebraic specification language? The hidden-sorted approach, originating in work of Goguen and Meseguer in the early 80's, and further developed into the hidden-sorted logic approach by researchers at Oxford, UC San Diego, and Kanazawa offers some attractive answers, and has been implemented in both BOBJ and CafeOBJ. In this work we investigate both further extensions of hidden logic, and an extension of the Maude specification language called BMaude supporting this extended hidden-sorted semantics.Maude's underlying equational logic, membership equational logic, generalizes and increases the expressive power of many-sorted and order-sorted equational logics. We develop a hidden-sorted extension of membership equational logic, and give conditions under which theories have both an algebraic and a coalgebraic semantics, including final (co-)algebras. We also discuss the language design of BMaude, based on such an extended logic and using categorical notions in and across the different institutions involved. We also explain how Maude's reflective semantics provides a systematic method to extend Maude to BMaude within Maude, including module composition operations, evaluation, and automated proof methods.     

一个面向网络计算的代码迁移性能模型

引入了面向网络计算的代码迁移概念及其三种计算模式。在定性分析了代码迁移模式与传统的Client／Server模式各自所适宜的应用背景及性能之后，建立了应用性能的定量分析模型。并通过一个例子示范性地阐明了定量分析的过程，为正确选择应用开发模式提供了参考。     

一个面向网络计算的代码迁移性能模型

引入了面向网络计算的代码迁移概念及其三种计算模式。在定性分析了代码迁移模式与传统的Client/Server模式各自所适宜的应用背景及性能之后,建立了应用性能的定量分析模型。并通过一个例子示范性地阐明了定量分析的过程,为正确选择应用开发模式提供了参考。     

基于卫星通信的网络移动建模与性能仿真

网络移动是指一个移动IP网络能够在保证通信连接不中断的条件下改变到一个IP骨干网的连接点,从而解决整个网络在移动过程中的不间断数据传输问题.采用卫星通信网实现移动网络的数据传输可以提供足够的带宽和更大的覆盖范围,是一种比较经济、可行的解决方案.首先建立了基于卫星通信的网络移动通信系统模型并在NS2软件中实现了该模型,然后基于该模型对TCP的性能以及切换对其性能的影响进行了仿真,最后通过分析卫星通信的特点提出了一种改进的切换策略.仿真结果表明,该策略可以显著减少切换引起的TCP中断时间.     

移动Ad Hoc网络模糊逻辑移动预测路由算法

移动自组网是一种能够支持多跳的临时性计算机通信网络.它由一组带有无线收发装置的移动节点组成.节点能随机任意移动,可导致拓扑的动态变化,会对路由的稳定性乃至网络的整体性能产生重要的影响.通过对节点运动速度和运动方向的观察,使用模糊逻辑控制策略,提出了一种基于模糊逻辑预测链路稳定性的路由算法.仿真结果表明,该协议有效地提高了数据连接的平均存活时间、链路的数据传输率和端到端的吞吐量,同时减小了端到端的延迟和控制的开销.     

带模糊控制的动态指针推进移动性管理策略

移动性管理是移动计算研究领域的一个挑战性课题.提出了一种带模糊控制器的动态指针推进移动性管理策略.这种策略以移动台的移动次数、指针链长度及位置管理的代价作为模糊控制器的输入,指针长度的改变量作为模糊控制器的输出,对指针长度进行动态调整.仿真实验结果表明：当移动台的呼入移动比较低时,这种策略比现行无线移动通信网络的移动性管理策略的性能更优.     

Strong Paraconsistency and the Basic Constructive Logic for an Even Weaker Sense of Consistency

In a standard sense, consistency and paraconsistency are understood as the absence of any contradiction and as the absence of the ECQ (‘E contradictione quodlibet’) rule, respectively. The concepts of weak consistency (in two different senses) as well as that of F-consistency have been defined by the authors. The aim of this paper is (a) to define alternative (to the standard one) concepts of paraconsistency in respect of the aforementioned notions of weak consistency and F-consistency; (b) to define the concept of strong paraconsistency; (c) to build up a series of strongly paraconsistent logics; (d) to define the basic constructive logic adequate to a rather weak sense of consistency. All logics treated in this paper are strongly paraconsistent. All of them are sound and complete in respect a modification of Routley and Meyer’s ternary relational semantics for relevant logics (no logic in this paper is relevant).     

移动支持协议移动管理代价研究

针对移动支持协议的移动管理代价进行了研究,提出了一种合适的网络模型.在此网络模型的基础上,采用理论分析的方法分析了使用各移动支持协议时,为支持MH(mobile host)移动给网络带来的信令开销,并采用数值仿真的方法,对只使用移动IP协议和引入层次移动时的信令开销以及采用MIP-RR,CIP和HAWAII等不同微移动协议时的信令开销进行了比较.结果表明:引入层次移动与只使用移动IP相比,显著减少了网络的信令开销;在不同的微移动协议中,使用显式删除旧路径的路径维护策略与频繁发送周期性的刷新报文相比,给网络带来的信令开销较小;使用路径更新报文发送到交叉MRA(mobile routing Agent)的路径更新方法与路径更新报文发送到GW(gateway)相比,具有较小的网络信令开销.     

移动支持协议切换性能研究

切换是移动支持协议研究的重要内容,其性能好坏对移动网络的性能和服务质量提供具有至关重要的影响.在合适的网络模型和切换模型的基础上,通过理论分析和数值仿真的方法对各类移动支持协议(包括移动IP与微观移动协议以及不同的微观移动协议)的切换性能进行了深入的研究和比较.结果表明,切换性能受无线网络参数和移动支持协议的路径更新算法两个因素影响;采用微观移动协议时的切换性能好于只使用移动IP时的情形;在所有微观移动协议中,MIP-RR和MMP协议中的路径更新算法切换性能最佳.     

基于泛逻辑学的柔性命题逻辑研究

现有的数理逻辑是刚性逻辑，不能满足研究不确定性问题的需要．概率测度是研究不确定性问题的重要数学工具．但作为概率推理理论基础的概率逻辑发展不够成熟，影响了它在不确定性推理中的广泛应用．本文第二作者在探索包含确定性和各种不确定性的现实世界逻辑规律的基础上．建立一个包容刚性逻辑和柔性逻辑的命题泛逻辑学体系．本文利用这一研究成果，对命题概率逻辑进行了探讨．     

Stochastic Ambient Calculus

Mobile Ambients (MA) have acquired a fundamental role in modelling mobility in systems with mobile code and mobile devices, and in computation over administrative domains. We present the stochastic version of Mobile Ambients, called Stochastic Mobile Ambients (SMA), where we extend MA with time and probabilities. Inspired by previous models, PEPA and Sπ, we enhance the prefix of the capabilities with a rate and the ambient with a linear function that operates on the rates of processes executing inside it. The linear functions associated with ambients represent the delays that govern particular administrative domains. We derive performance measures from the labelled transition semantics as in standard models. We also define a strong Markov bisimulation in the style of reduction semantics known as barbed bisimulation. We argue that performance measures are of vital importance in designing any kind of distributed system, and that SMA can be useful in the design of the complicated mobile systems.     

The Complexity of Modellability in Finite and Computable Signatures of a Constraint Logic for Head-Driven Phrase Structure Grammar

The SRL (speciate re-entrant logic) of King (1989) is a sound, complete and decidable logic designed specifically to support formalisms for the HPSG (head-driven phrase structure grammar) of Pollard and Sag (1994). The SRL notion of modellability in a signature is particularly important for HPSG, and the present paper modifies an elegant method due to Blackburn and Spaan (1993) in order to prove that

Paraconsistent Declarative Semantics for Extended Logic Programs

We introduce a fixpoint semantics for logic programs with two kinds of negation: an explicit negation and a negation-by-failure. The programs may also be prioritized, that is, their clauses may be arranged in a partial order that reflects preferences among the corresponding rules. This yields a robust framework for representing knowledge in logic programs with a considerable expressive power. The declarative semantics for such programs is particularly suitable for reasoning with uncertainty, in the sense that it pinpoints the incomplete and inconsistent parts of the data, and regards the remaining information as classically consistent. As such, this semantics allows to draw conclusions in a non-trivial way, even in cases that the logic programs under consideration are not consistent. Finally, we show that this formalism may be regarded as a simple and flexible process for belief revision.