Lexically scoped distribution: what you see is what you get

We define a lexically scoped, asynchronous and distributed π-calculus, with local communication and process migration. This calculus adopts the network-awareness principle for distributed programming and follows a simple model of distribution for mobile calculi: a lexical scope discipline combines static scoping with dynamic linking, associating channels to a fixed site throughout computation. This discipline provides for both remote invocation and process migration. A simple type system is a straightforward extension of that of the π-calculus, adapted to take into account the lexical scope of channels. An equivalence law captures the essence of this model: a process behavior depends on the channels it uses, not on where it runs.     

On the Expressiveness of Chi, Update, and Fusion calculi

Chi and Update calculi [9,17] have been independently introduced in order to model mobile systems. The two calculi are very close to each other and represent an evolution of π-calculus [15]. More recently a (non-straightforward) polyadic version of the Update calculus, the Fusion calculus, has been proposed [18].In the paper we give a fully abstract encoding from an asynchronous variant of Chi and Update calculi to asynchronous π-calculus [11,4]. This proves that, at least for their asynchronous variants, Chi and Update calculi are not more expressive than π-calculus. A similar result can be proved for the Fusion calculus.     

Beta-binders for Biological Quantitative Experiments

The similarities between biological systems and distributed and mobile systems suggest that the theory of process calculi could be a useful starting point for understanding, if not predicting, the behaviour of complex biological systems.To formally model in vitro or in vivo experiments, appropriate quantitative extensions of process calculi have to be investigated. This paper focuses on Beta-binders, a language of processes with typed interaction sites which has been recently introduced to accurately represent biological entities.Here the syntax and semantics of Beta-binders are enriched to achieve a stochastic version of it, in order to obtain quantitative measures on biological phenomena. The quantitative parameters are derived from typed interaction sites introducing the concept of affinity. The relevance of quantitative reasoning is outlined running a biological example.     

Reliable distributed data stream management in mobile environments

The proliferation of sensor technology, especially in the context of embedded systems, has brought forward novel types of applications that make use of streams of continuously generated sensor data. Many applications like telemonitoring in healthcare or roadside traffic monitoring and control particularly require data stream management (DSM) to be provided in a distributed, yet reliable way. This is even more important when DSM applications are deployed in a failure-prone distributed setting including resource-limited mobile devices, for instance in applications which aim at remotely monitoring mobile patients. In this paper, we introduce a model for distributed and reliable DSM. The contribution of this paper is threefold. First, in analogy to the SQL isolation levels, we define levels of reliability and describe necessary consistency constraints for distributed DSM that specify the tolerated loss, delay, or re-ordering of data stream elements, respectively. Second, we use this model to design and analyze an algorithm for reliable distributed DSM, namely efficient coordinated operator checkpointing (ECOC). We show that ECOC provides lossless and delay-limited reliable data stream management and thus can be used in critical application domains such as healthcare, where the loss of data stream elements cannot be tolerated. Third, we present detailed performance evaluations of the ECOC algorithm running on mobile, resource-limited devices. In particular, we can show that ECOC provides a high level of reliability while, at the same time, featuring good performance characteristics with moderate resource consumption.     

Formalising Java RMI with explicit code mobility

This paper presents an object-oriented, Java-like core language with primitives for distributed programming and explicit code mobility. We apply our formulation to prove the correctness of several optimisations for distributed programs. Our language captures crucial but often hidden aspects of distributed object-oriented programming, including object serialisation, dynamic class downloading and remote method invocation. It is defined in terms of an operational semantics that concisely models the behaviour of distributed programs using machinery from calculi of mobile processes. Type safety is established using invariant properties for distributed runtime configurations. We argue that primitives for explicit code mobility offer a programmer fine-grained control of type-safe code distribution, which is crucial for improving the performance and safety of distributed object-oriented applications.     

Tile Formats for Located and Mobile Systems

Standard SOS formats are limited in their ability to define the operational semantics of process calculi with concurrency, causality, and mobility, and with bound names and name generation mechanisms. In this paper we describe a general approach, based on the tile model, to the definition of the operational semantics of process calculi. By providing tile systems for located CCS and asynchronous π-calculus we demonstrate that the proposed approach is more suited than SOS to provide a uniform treatment of concurrency and mobility within a compositional framework.     

Implementing distributed control system for intelligent mobile robot

The control system of a mobile robot has a number of issues to deal with in real time, including motion control, mapping, localization, path planning, and sensor processing. Intelligent reasoning, task-oriented behaviors, human–robot interfaces, and communications add more tasks to be solved. This naturally leads to a complex hierarchical control system where various tasks have to be processed concurrently. Many low-level tasks can be handled by a robots onboard (host) computer. However, other tasks, such as speech recognition or vision processing, are too computationally intensive for one computer to process. In this case, it is better to consider a distributed design for the control system in networked environments. In order to achieve maximum use of the distributed environment, it is important to design and implement the distributed system and its communication mechanisms in an effective and flexible way. This article describes our approach to designing and implementing a distributed control system for an intelligent mobile robot. We present our implementation of such a distributed control system for a prototype mobile robot. We focus our discussion on the system architecture, distributed communication mechanisms, and distributed robot control.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

Calculi of meta-variables

The notion of meta-variable plays a fundamental role when we define formal systems such as logical and computational calculi. Yet it has been usually understood only informally as is seen in most textbooks of logic. Based on our observations of the usages of metavariables in textbooks, we propose two formal systems that have the notion of meta-variable. In both calculi, each variable is given a level (non-negative integer), which classifies variables into object variables (level 0), meta-variables (level 1), metameta-variables (level 2) and so on. Then, simple arity systems are used to exclude meaningless terms like a meta-level function operating on the metameta-level. A main difference of the two calculi lies in the definitions of substitution. The first calculus uses textual substitution, which can often be found in definitions of quantified formulae: when a term is substituted for a meta-variable, free object-level variables in the term may be captured. The second calculus is based on the observation that predicates can be regarded as meta-level functions on object-level terms, hence uses capture-avoiding substitution. We show that both calculi enjoy a number of properties including Church-Rosser and Strong Normalization, which are indispensable when we use them as frameworks to define logical systems.     

Calculi of meta-variables

The notion of meta-variable plays a fundamental role when we define formal systems such as logical and computational calculi. Yet it has been usually understood only informally as is seen in most textbooks of logic. Based on our observations of the usages of metavariables in textbooks, we propose two formal systems that have the notion of meta-variable. In both calculi, each variable is given a level (non-negative integer), which classifies variables into object variables (level 0), meta-variables (level 1), metameta-variables (level 2) and so on. Then, simple arity systems are used to exclude meaningless terms like a meta-level function operating on the metameta-level. A main difference of the two calculi lies in the definitions of substitution. The first calculus uses textual substitution, which can often be found in definitions of quantified formulae: when a term is substituted for a meta-variable, free object-level variables in the term may be captured. The second calculus is based on the observation that predicates can be regarded as meta-level functions on object-level terms, hence uses capture-avoiding substitution. We show that both calculi enjoy a number of properties including Church-Rosser and Strong Normalization, which are indispensable when we use them as frameworks to define logical systems.     

Distributed information service architecture for overlapping multiaccess networks

Multimedia delivery in mobile multiaccess network environments has emerged as a key area within the future Internet research domain. When network heterogeneity is coupled with the proliferation of multiaccess capabilities in mobile handheld devices, one can expect many new avenues for developing novel services and applications. New mechanisms for audio/video delivery over multiaccess networks will define the next generation of major distribution technologies, but will require significantly more information to operate according to their best potential. In this paper we present and evaluate a distributed information service, which can enhance media delivery over such multiaccess networks. We describe the proposed information service, which is built upon the new distributed control and management framework (DCMF) and the mobility management triggering functionality (TRG). We use a testbed which includes 3G/HSPA, WLAN and WiMAX network accesses to evaluate our proposed architecture and present results that demonstrate its value in enhancing video delivery and minimizing service disruption in an involved scenario.     

Display Calculi for Logics with Relative Accessibility Relations

We define cut-free display calculi for knowledge logics wherean indiscernibility relation is associated to each set of agents, andwhere agents decide the membership of objects using thisindiscernibility relation. To do so, we first translate the knowledgelogics into polymodal logics axiomatised by primitive axioms and thenuse Kracht's results on properly displayable logics to define thedisplay calculi. Apart from these technical results, we argue thatDisplay Logic is a natural framework to define cut-free calculi for manyother logics with relative accessibility relations.     

基于CORBA技术的程控交换机控制系统的设计与实现

移动通信系统中程控交换机类型众多，为了对分散的交换机群移动业务进行集成控制和管理，实现开放的平台，该文引入了CORBA来实现程控交换机服务控制的中间层，同时介绍了CORBA的对象模型，阐述了运用CORBA实现程控交换机控制系统的工作原理及过程。     

Incremental Q-learning strategy for adaptive PID control of mobile robots

Expert and intelligent systems are being developed to control many technological systems including mobile robots. However, the PID (Proportional-Integral-Derivative) controller is a fast low-level control strategy widely used in many control engineering tasks. Classic control theory has contributed with different tuning methods to obtain the gains of PID controllers for specific operation conditions. Nevertheless, when the system is not fully known and the operative conditions are variable and not previously known, classical techniques are not entirely suitable for the PID tuning. To overcome these drawbacks many adaptive approaches have been arisen, mainly from the field of artificial intelligent. In this work, we propose an incremental Q-learning strategy for adaptive PID control. In order to improve the learning efficiency we define a temporal memory into the learning process. While the memory remains invariant, a non-uniform specialization process is carried out generating new limited subspaces of learning. An implementation on a real mobile robot demonstrates the applicability of the proposed approach for a real-time simultaneous tuning of multiples adaptive PID controllers for a real system operating under variable conditions in a real environment.     

Parametric synchronizations in mobile nominal calculi

We present and compare P-PRISMA and F-PRISMA, two parametric calculi that can be instantiated with different interaction policies, defined as synchronization algebras with mobility of names (SAMs). In particular, P-PRISMA is based on name transmission (P-SAM), like π-calculus, and thus exploits directional (input–output) communication only, while F-PRISMA is based on name fusion (F-SAM), like Fusion calculus, and thus exploits a more symmetric form of communication. However, P-PRISMA and F-PRISMA can easily accommodate many other high-level synchronization mechanisms than the basic ones available in π-calculus and Fusion, hence allowing for the development of a general meta-theory of mobile calculi. We define for both the labeled operational semantics and a form of strong bisimilarity, showing that the latter is compositional for any SAM. We also discuss reduction semantics and weak bisimilarity. We give several examples based on heterogeneous SAMs, we investigate the case studies of π-calculus and Fusion calculus giving correspondence theorems, and we show how P-PRISMA can be encoded in F-PRISMA. Finally, we show that basic categorical tools can help to relate and to compose SAMs and PRISMA processes in an elegant way.     

Achieving Mobile Agent Systems interoperability through software layering

Interoperability is a key issue for a wider adoption of mobile agent systems (MASs) in heterogeneous and open distributed environments where agents, in order to fulfill their tasks, must interact with non-homogeneous agents and traverse different agent platforms to access remote resources. To date, while several approaches have been proposed to deal with different aspects of MAS interoperability, they all lack the necessary flexibility to provide an adequate degree of interoperability among the currently available MASs. In this paper, we propose an application-level approach grounded in the software layering concept, which enables execution, migration and communication interoperability between Java-based mobile agent systems, thus overcoming major setbacks affecting the other approaches currently proposed for supporting MAS interoperability. In particular, we define a Java-based framework, named JIMAF, which relies on an event-driven, proxy-based mobile agent model and supports interoperable mobile agents which can be easily coded and adapted to existing MASs without any modifications of the MAS infrastructures. Results from the performance evaluation of MAS interoperability was carried by using JIMAF atop Aglets, Ajanta, Grasshopper, and Voyager, demonstrating that the high-level JIMAF approach offers high efficacy while maintaining overhead at acceptable levels for target computing environments.     

On the Computational Representation of Classical Logical Connectives

Many programming calculi have been designed to have a Curry-Howard correspondence with a classical logic. We investigate the effect that different choices of logical connective have on such calculi, and the resulting computational content.We identify two connectives 'if-and-only-if' and 'exclusive or' whose computational content is not well known, and whose cut elimination rules are non-trivial to define. In the case of the former, we define a term calculus and show that the computational content of several other connectives can be simulated. We show this is possible even for connectives not logically expressible with 'if-and-only-if'.     

Controlling energy without compromising system performance in mobile grid environments

The challenges confronting in mobile grid systems are: limited CPU power, limited memory, small screen, short battery life, and intermittent disconnection. Considering all these limitations, this paper is targeted to control energy consumption without compromising system’s performance in mobile grid. In this paper, we focus on using the mobile devices on the mobile grid environment. Mobile devices can serve two important functions in mobile grid environment either as service consumer or as valuable service providers. The proposed approach is not only to reduce energy consumption, but also to improve system performance in mobile grid environment. Utility functions are used to express grid users’ requirements, resource providers’ benefit function and system’s objectives. Dynamic programming is used to optimize the total utility function of mobile grid. A distributed controlling energy algorithm in mobile grid environment is proposed which decomposes mobile grid system optimization problem into sub-problems. In order to verify the efficiency of the proposed algorithm, in the experiment, the performance evaluation of controlling energy algorithm is conducted.     

移动实时嵌套事务的并发控制

在移动计算环境中，事务移动性和无线网络固有的缺陷使得传统分布式实时事务管理机制不足以支持移动实时事务的执行，故有必要为移动实时事务研究新的事务处理机制以提高其成功率．该文着重研究移动实时事务的并发控制机制．首先，该文给出了一个考虑事务定时限制以及移动性的嵌套事务模型．然后，为减少移动分布式环境中解决数据冲突的开销，该文研究了一种结合优先级夭折和优先级继承的基于封锁的并发控制协议PAI-2PL．当高优先级事务被低优先级事务阻塞时，对于相同家族事务，采用优先级继承方法解决冲突；而对于不同家族事务，则夭折重启低优先级事务．另外，为减少由于断接所引起的无效阻塞，PAI-2PL允许低优先级事务夭折处于断接状态的高优先级事务．通过性能测试，表明所提出的事务模型及并发控制机制能提高实时事务的成功率．     

A taxonomy of process calculi for distribution and mobility

In this paper, we comparatively analyze some mainstream calculi for mobility and distribution, together with some of their variants: asynchronous π-calculus, distributed π-calculus, and some dialects of Mobile/Boxed/Safe ambients. In particular, we focus on their relative expressive power, i.e. we try to encode every language in the other while respecting some reasonable properties. According to the possibility or the impossibility for such results, we set up a taxonomy of these languages. Our study enables understanding, for every pair of calculi, which features of one can be rendered in the other and how this is possible, or which features cannot be rendered and why this is impossible.     

Formal analysis of seamless application execution in mobile cloud computing

Mobile cloud computing augments the resource-constrained mobile devices to run rich mobile applications by leveraging the cloud resources and services. Compute-intensive mobile apps require significant communication resources for migrating the code from mobile devices to the cloud. For such apps, distributed application execution frameworks (DAEF) have been proposed in the literature. These frameworks either migrate the mobile app code during runtime or keep the app synchronized with another remotely executed app on the cloud. Frameworks also support mobile app live migration to cater for compute node mobility. One key research question arises is how successful are these DAEFs in achieving the seamless application execution under various network conditions? The answer to this question entails formal analysis of the DAEFs to determine the realistic bounds on propagation delay, bandwidth and application interaction with mobile device for various types and sizes of apps. In this research, we apply formal analysis techniques to define the execution time of the app and the time required for code migration. We also define three conditions for seamless application execution. Given realistic values for processor speed, application executable size, possible number of executed instructions, network propagation delay and transmission delay, we show what components of the mobile app need to be migrated during execution to the cloud. Finally, we compute realistic bounds for the app size (that can be executed seamlessly) based on important features which include cloud and device resources, bandwidth and latency profile.