A Notation and Logic for Mobile Computing

We define a concurrent mobile system as one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. The definition is general enough to encompass a system of mobile hosts moving in physical space as well as a system of migrating software agents implemented on a set of possibly non-mobile hosts. In this paper, we present Mobile UNITY, a notation for expressing mobile computations and a logic for reasoning about their temporal properties. Our goal is to find a minimalist model of mobile computation that will allow us to express mobile components in a modular fashion and to reason formally about the possible behaviors of a system composed from mobile components. A simplified serial communication protocol among components which can move in space serves as an illustration for the notation.     

移动Agent系统的服务动态部署研究

通过使用移动Agent,分布式应用可以像一组可移动的松耦合的组件那样执行它们的功能。因此可以做出模块化并且可扩展的设计。但是,目前的大多数移动Agent平台的扩展性并不好,平台配置之后往往就很难再改变。为此,在动态配置的支持下为移动Agent设计了一个基于组件的框架,使得组件可以在运行时被增加、移动和改动,为构建一个高适应性的移动Agent平台提供了可能。     

Reasoning about places, times, and actions in the presence ofmobility

The current trend toward portable computing systems (e.g., cellular phones, laptop computers) brings with it the need for a new paradigm to facilitate thinking about and designing distributed applications. We use the term mobile to refer to distributed systems that include moving, autonomous agents which loosely cooperate to accomplish a task. The fluid nature of the interconnections among components of a mobile system provides new challenges and opportunities for the research community. While we do not claim to have fully grasped all the issues involved in specifying and modeling such systems, we believe that the notions of place, time, and action will play a central role in any model that is developed. We show that these concepts can be expressed and reasoned about in the UNITY logic with a minimal amount of additional notation. The formal derivation of a control system for a radio-dispatched elevator is used to show how considerations involving place, time, and actions impact the design process, be it formal or semiformal     

Programming for modular reconfigurable robots

Composed of multiple modular robotic units, self-reconfigurable modular robots are metamorphic systems that can autonomously rearrange the modules and form different configurations depending on dynamic environments and tasks. The goal of self-reconfiguration is to determine how to change connectivity of modules to transform the robot from the current configuration to the goal configuration subject to restrictions of physical implementation. The existing reconfiguration algorithms use different methods, such as divide-and-conquer, graph matching, and the like, to reduce the reconfiguration cost. However, an optimal solution with a minimal number of reconfiguration steps has not been found yet. The optimal reconfiguration planning problem consists in finding the least number of reconfiguration steps transforming the robot from one configuration to another. This is an NP-complete problem. In this paper, we describe an approach to solve this problem. The approach is based on constructing logical models of the problem under study.     

Structural reconfiguration of systems under behavioral adaptation

A major asset of modern systems is to dynamically reconfigure themselves to cope with failures or component updates. Nevertheless, designing such systems with off-the-shelf components is hardly feasible: components are black-boxes that can only interact with others on compatible interfaces. Part of the problem is solved through Software Adaptation techniques, which compensate mismatches between interfaces. Our approach aims at using results of Software Adaptation in order to also provide reconfiguration capabilities to black-box components.This paper first formalizes a framework that unifies behavioral adaptation and structural reconfiguration of components. This formalization is used for statically detecting whether it is possible to reconfigure a system. In a second part, we present five notions of reconfiguration: history-aware reconfiguration, future-aware reconfiguration, property-compliant reconfiguration, one-way reconfigurability, and full reconfigurability. For each of these notions, its relevant properties are presented, and they are illustrated on simple yet realistic examples.     

Connectors for mobile programs

Software architecture has put forward the concept of connector to express complex relationships between system components, thus facilitating the separation of coordination from computation. This separation is especially important in mobile computing due to the dynamic nature of the interactions among participating processes. We present connector patterns, inspired in Mobile UNITY, that describe three basic kinds of transient interactions: action inhibition, action synchronization, and message passing. The connectors are given in COMMUNITY, a UNITY-like program design language which has a semantics in category theory. We show how the categorical framework can be used for applying the proposed connectors to specific components and how the resulting architecture can be visualized by a diagram showing the components and the connectors     

Compositional and behavior-preserving reconfiguration of component connectors in Reo

It is generally accepted that building software out of loosely coupled components, such as in service-oriented systems or mobile networks, yields applications that are more robust against changes and failure of single components than monolithic systems. In order to accommodate for changes in the environment or in the requirements, and anticipate to a component failure, applications are often dynamically adapted by means of a reconfiguration. In this paper, we target the visual channel-based coordination language Reo and introduce a combined structural and behavioral model for graph-based component connectors in Reo. Exploiting concepts from category theory, we model reconfigurations of connectors as transformations of the underlying connector graphs. We show that our connector model has a compositional semantics and lift structural reconfigurations to the semantical level. As a concrete application of our framework, we introduce a notion of behavior-preserving reconfiguration for Reo and provide a sufficient condition to ensure behavior-preservation statically.     

An architecture for universal construction via modular robotic components

A set of modular components is presented for use in reconfigurable robotic construction systems. The set includes passive and active components. The passive components can be formed into static structures and adaptable grids carrying electrical power and signals. Passive and active components can be combined into general purpose mobile manipulators which are able to augment and reconfigure the grid, construct new manipulators, and potentially perform general purpose fabrication tasks such as additive manufacturing. The components themselves are designed for low-cost, simple fabrication methods and could potentially be fabricated by constructors made of the same components. This work represents a step toward a Cyclic Fabrication System, a network of materials, tools, and manufacturing processes that can produce all of its constituent components. These and similar systems have been proposed for a wide range of far-term applications, including space-based manufacturing, construction of large-scale industrial facilities, and also for driving development of low-cost 3D printing machines.     

Intelligent Reconfiguration of Dynamic Distributed Components

Naming service and the reconfiguration management systems usually work in a client-server manner where both the selection of components and the reconfiguration are a result of a request. Developing intelligent systems that are capable of monitoring and learning about themselves, and thereby rapidly react to changes in their environment, has become essential to most systems. This paper proposes an extension to FRODICA (Framework for Distributed Configurable Applications), a framework that supports the development of non-functional oriented reconfiguration of distributed systems, using the Complex Organic Distributed Architecture (CODA). CODA applies cybernetic concepts such as self-organisation, self-regulation and viability to derive an intelligent architecture, which can react to failures in achieving its objectives and proactively search for successful patterns of behaviour. The result is a configuration management system, which can use the knowledge of itself to proactively and dynamically drive both the search and the reconfiguration of its components.     

Combinatorial optimization in system configuration design

The significance of systems configurations has been increased in many applied domains (e.g., software, hardware, manufacturing systems, communication systems, supply chain systems, solving strategies, modular planning, material engineering and combinatorial chemistry). Generally, the following kinds of systems under configuration (reconfiguration) can be examined: (a) initial data/infomation (or row materials); (b) processing systems (machines, computers, algorithms); (c) resultant decisions (e.g., products, plans); (d) applied support systems (e.g., network systems, services); (e) requirements; and (f) standards. In the paper several system configuration problems are investigated: (i) searching for (selection of) a set (structure) of system components, (ii) searching for a set of compatible system components, (iii) allocation of system components, (iv) reconfiguration of a system as redesign of the system structure, (v) multi-stage design and redesign of system configuration, (vi) design or redesign of the system configuration for multi-product systems, and (vii) design of system hierarchy. Combinatorial optimization models (including multicriteria statements) are under examination: multiple choice problem, allocation problem, graph coloring problems, morphological clique problem (with compatibility of system components), multipartite clique and their modifications, spanning trees problems.     

可重构制造系统监督控制器的自动重构

提出了基于改进的网重写系统(Improved net rewriting system, INRS)的可重构制造系统(Reconfigurable manufacturing systems, RMS) Petri网监督控制器的自动重构方法, 以快速适应由市场需求变化所引起的制造系统构形的频繁变化. INRS解决了网重写系统存在的问题, 可动态调整给定Petri网模型的结构而不改变其行为属性. 以集合和图的组合形式定义了RMS的构形, 并提出了基于INRS的一类模块化、可重构的Petri网控制器的设计方法. 针对这类Petri网控制器, 提出了基于INRS的自动重构方法. 方法可将RMS构形的变化转变为INRS的图重写规则, 并作用于当前Petri网控制器, 使其快速、自动地重构为所求的新控制器. 所提出的Petri网控制器的设计与重构方法, 均从理论上保证了结果的正确性, 免校验. 仿真研究验证了方法的有效性.     

一种新型的双频段圆极化可重构微带天线

在移动终端的狭小受限空间内,如何有效地利用频率资源、空间资源,提高通信系统的传输容量是研究热点,设计性能良好的可重构天线是一种有效手段。本文采用多环缝隙结构设计了一种新型的双频段圆极化可重构天线。它在MEMS开关的控制下,可在4.9GHz和5.8GHz两个频率上同时实现左旋和右旋圆极化,两个频带的相对带宽分别达到11.2%和13.8%,很好地实现了圆极化可重构天线的双频带特性,能够满足移动通信对多频技术的需求。     

Gradient-based multi-component topology optimization for stamped sheet metal assemblies (MTO-S)

A collection of interacting systems, such as a fleet of military vehicles, can have a life-cycle benefit from sharing interoperable modules. Defining the modules that maximize such benefits must be addressed at the early stages of system design. We present a multi-objective optimization framework for conceptual modular design. We use a functional representation of the supersystem, i.e., the interacting systems collection, to make module design decisions informed by supersystem requirements and life-cycle objectives. The resultant modules are configured into a variety of architectures and form a set of systems with distinct capabilities that meet supersystem requirements. We apply this approach on a fleet of military vehicles. Computational results quantify the intuition that designing a large number of smaller modules reduces overall fleet weight and increases required personnel resources because of larger demand for vehicle reconfiguration.     

Ontology-based reconfiguration agent for intelligent mechatronic systems in flexible manufacturing

This paper proposes a novel approach to achieving fast reconfiguration of modular manufacturing systems, based on an ontology-based reconfiguration agent. The agent uses ontological knowledge of the manufacturing environment for the purpose of reconfiguration without human intervention. The current mass customization era requires increased flexibility and agility in the manufacturing systems to adapt changes in manufacturing requirements and environments. Our configuration agent minimises the overheads of the current reconfiguration process by automating it. It infers facts about the manufacturing environment from the ontological knowledge model and then decides whether the current environment can support the given manufacturing requirements. This paper proposes the agent architecture enabling the integration between the high level planning with the distributed low level control compliant with the upcoming IEC 61499 function blocks standard.     

Compositional Comparison of Formal Software Specifications Using Transformation Systems

In a model-based software systems development formal specifications of the components of the system are developed. Thereby different specifications are used to represent the different aspects or views of the components, possibly following different paradigms. These heterogeneous viewpoint specifications have to be integrated in order to obtain a consistent global specification of the whole system. In this paper transformation systems are introduced as a common semantic domain where specifications written in different languages can be interpreted and formally compared. A transformation system is a transition system where the transitions are labelled by sets of actions and the states are labelled by algebras representing the data states. Development relations and composition operations for transformation systems are investigated, and it is shown that compatible local developments of components induce a global development of their composition. As an application two specifications of the alternating bit protocol are formally compared component-wise, one given in the process calculus CCS, the other one in the parallel programming language UNITY. Received September 2000 / Accepted in revised form June 2001     

A contract-based approach to adaptivity

Adaptive systems are systems capable of adapting their behaviour to changes in their environment. Creating such systems is not an easy task, however. Especially, creating such a system as one monolithic software component taking all eventualities and environments into account bears the risk of bad system design. To circumvent this risk, an adaptive system can be composed from partial solutions handling only a subset of all possible circumstances and environments. Then, the system can be changed through reconfigurations as the environment evolves. In this paper, we propose an approach for the verification of systems using reconfiguration as means of adaptation. For the specification of such systems and their components we introduce reMitl which is based on Metric Interval Temporal Logic Mitl and allows to express connectivity of components. Based on an example from the domain of pervasive computing, we show how a system undergoing reconfigurations can be verified to satisfy a global assume-guarantee contract expressed as a pair of reMitl formulas.     

PRO-MOTION: Support for mobile database access

In order to provide data consistency in the presence of failures and concurrency, database methods will continue to be important to the processing of shared information in a mobile computing environment. It is important, therefore, that we develop transaction processing systems that accommodate the limitations of mobile computing, such as frequent disconnection, limited battery life, low-bandwidth communication and reduced storage capacity, so that we can migrate existing database applications to mobile environments. In this paper, motivated by these needs, we propose a mobile transaction processing system that supports disconnected transaction processing in a mobile client-server environment. The proposed system employs compacts, which encapsulate access methods, state information and consistency constraints, to allow for local management of database transactions on mobile computers.