并发面向对象语言COOLⅡ的语义模型

缺乏好的形式化语义模型使得并发面向对象语言的开发受到了很大的影响,本文设计了并发面向对象LISP语言COOLⅡ,给出了该语言的语法、基于配置的操作语义,并提出了并发对象演算CONOC,以此为基础讨论了COOLⅡ的变换语义。     

具有并发类库的C++

本文探讨如何通过类库将并发性引入顺序面向对象语言.以C++为例,在并发类库中提供并发类及相应工具,使之支持分布并行的面向对象程序设计.本文介绍并发类库及语言底层支撑系统的设计与实现,最后给出初步测试结果.     

Gout-ITS系统的正向启发式推理算法

分析了痛风临床诊治智能教学系统（intelligent tutoring system for instruction of gout clinical diagnosis and treatment,Gout-ITS）要像人类医疗专家那样进行临床诊治推理所需的领域知识及其特点,提出了知识库的层次结构模型和正向启发式推理算法。该算法不仅能够对病例做出正确的诊断和有效的治疗,而且还能够使诊治代价降至最小。最后将该算法与一般产生式系统的正向推理算法进行了比较,阐述了该算法的优点。     

一个移动进程演算的互模拟同余定义框架

并发计算模型是理论计算机科学研究的重要领域之一。以π演算为代表的移动进程演算是目前并发理论的研究热点。互模拟等价定义是移动进程演算研究中的核心概念和问题,而传名机制使得移动进程演算中的互模拟同余关系更加复杂和有趣。本文在分析了常见的互模拟同余定义的基础上,通过抽取定义的核心要素,提出了一个三维的互模拟同余定义模型,从而将一般文献中常见的互模拟定义纳入到一个统一的框架中来,加深了我们对移动进程演算中互模拟概念的理解;同时本文利用这个模型,系统分析了各种互模拟之阿的关系。模型的优点在于它的普适性和开放性。     

Static type information to improve the IDE features of hybrid dynamically and statically typed languages

The flexibility offered by dynamically typed programming languages has been appropriately used to develop specific scenarios where dynamic adaptability is an important issue. This has made some existing statically typed languages gradually incorporate more dynamic features to their implementations. As a result, there are some programming languages considered hybrid dynamically and statically typed. However, these languages do not perform static type inference on a dynamically typed code, lacking those common features provided when a statically typed code is used. This lack is also present in the corresponding IDEs that, when a dynamically typed code is used, do not provide the services offered for static typing. We have customized an IDE for a hybrid language that statically infers type information of dynamically typed code. By using this type information, we show how the IDE can provide a set of appealing services that the existing approaches do not support, such as compile-time type error detection, code completion, transition from dynamically to statically typed code (and vice versa), and significant runtime performance optimizations. We have evaluated the programmer׳s performance improvement obtained with our IDE, and compared it with similar approaches.     

Safe model polymorphism for flexible modeling

Domain-Specific Languages (DSLs) are increasingly used by domain experts to handle various concerns in systems and software development. To support this trend, the Model-Driven Engineering (MDE) community has developed advanced techniques for designing new DSLs. However, the widespread use of independently developed, and constantly evolving DSLs is hampered by the rigidity imposed to the language users by the DSLs and their tooling, e.g., for manipulating a model through various similar DSLs or successive versions of a given DSL. In this paper, we propose a disciplined approach that leverages type groups׳ polymorphism to provide an advanced type system for manipulating models, in a polymorphic way, through different DSL interfaces. A DSL interface, a.k.a. model type, specifies a set of features, or services, available on the model it types, and subtyping relations among these model types define the safe substitutions. This type system complements the Melange language workbench and is seamlessly integrated into the Eclipse Modeling Framework (EMF), hence providing structural interoperability and compatibility of models between EMF-based tools. We illustrate the validity and practicability of our approach by bridging safe interoperability between different semantic and syntactic variation points of a finite-state machine (FSM) language, as well as between successive versions of the Unified Modeling Language (UML).     

A practical approach to type inference for EuLisp

Lisp applications need to show a reasonable cost-benefit relationship between the offered expressiveness and their demand for storage and run-time. Drawbacks in efficiency, apparent inLisp as a dynamically typed programming language, can be avoided by optimizations. Statically inferred type information can be decisive for the success of these optimizations.This paper describes a practical approach to type inference realized in a module and application compiler forEuLisp. The approach is partly related to Milner-style polymorphic type inference, but differs by describing functions withgeneric type schemes. Dependencies between argument and result types can be expressed more precisely by using generic type schemes of several lines than by using the common one-line type schemes. Generic type schemes contain types of a refined complementary lattice and bounded type variables. Besides standard and defined types so-calledstrategic types (e.g. singleton, zero, number-list) are combined into the type lattice. Local, global and control flow inference using generic type schemes with refined types generate precise typings of defined functions. Due to module compilation, inferred type schemes of exported functions can be stored in export interfaces, so they may be reused when imported elsewhere.This work was supported by the German Federal Ministry for Research and Technology (BMFT) within the joint project APPLY. The partners in this project are the Christian Albrechts University Kiel, the Fraunhofer Institute for Software Engineering and Systems Engineering (ISST), the German National Research Centre for Computer Science (GMD), and VW-GEDAS.     

Type inference and strong static type checking for Promela

The Spin model checker and its specification language Promela have been used extensively in industry and academia to check the logical properties of distributed algorithms and protocols. Model checking with Spin involves reasoning about a system via an abstract Promela specification, thus the technique depends critically on the soundness of this specification. Promela includes a rich set of data types including first-class channels, but the language syntax restricts the declaration of channel types so that it is not generally possible to deduce the complete type of a channel directly from its declaration. We present the design and implementation of Etch, an enhanced type checker for Promela, which uses constraint-based type inference to perform strong type checking of Promela specifications, allowing static detection of errors that Spin would not detect until simulation/verification time, or that Spin may miss completely. We discuss theoretical and practical problems associated with designing a type system and type checker for an existing language, and formalise our approach using a Promela-like calculus. To handle subtyping between base types, we present an extension to a standard unification algorithm to solve a system of equality and subtyping constraints, based on bounded substitutions.     

Comparison of selected algorithms for scheduling workflow applications with dynamically changing service availability

This paper compares the quality and execution times of several algorithms for scheduling service based workflow applications with changeable service availability and parameters. A workflow is defined as an acyclic directed graph with nodes corresponding to tasks and edges to dependencies between tasks. For each task, one out of several available services needs to be chosen and scheduled to minimize the workflow execution time and keep the cost of service within the budget. During the execution ofa workflow, some services may become unavailable, new ones may appear, and costs and execution times may change with a certain probability. Rescheduling is needed to obtain a better schedule. A solution is proposed on how integer linear pro- gramming can be used to solve this problem to obtain optimal solutions for smaller problems or suboptimal solutions for larger ones. It is compared side-by-side with GAIN, divide-and-conquer, and genetic algorithms for various probabilities of service unavailability or change in service parameters. The algorithms are implemented and subsequently tested in a real BeesyCluster environment.     

DOPS——分布式面向对象编程系统

ＤＯＰＳ是我们在Ｓｕｎ工作站网络中设计实现的分布式面向对象编程系统。目前包括并发面向对象编程语言ＣＣ＋＋和该语言在松散耦合分布式环境中的运行支撑系统ＤＲＴＳ。本文分别介绍ＣＣ＋＋和ＤＲＴＳ的设计与实现，最后给出检测结果。     

Constraint programming for type inference in flexible model-driven engineering

Domain experts typically have detailed knowledge of the concepts that are used in their domain; however they often lack the technical skills needed to translate that knowledge into model-driven engineering (MDE) idioms and technologies. Flexible or bottom-up modelling has been introduced to assist with the involvement of domain experts by promoting the use of simple drawing tools. In traditional MDE the engineering process starts with the definition of a metamodel which is used for the instantiation of models. In bottom-up MDE example models are defined at the beginning, letting the domain experts and language engineers focus on expressing the concepts rather than spending time on technical details of the metamodelling infrastructure. The metamodel is then created manually or inferred automatically. The flexibility that bottom-up MDE offers comes with the cost of having nodes in the example models left untyped. As a result, concepts that might be important for the definition of the domain will be ignored while the example models cannot be adequately re-used in future iterations of the language definition process. In this paper, we propose a novel approach that assists in the inference of the types of untyped model elements using Constraint Programming. We evaluate the proposed approach in a number of example models to identify the performance of the prediction mechanism and the benefits it offers. The reduction in the effort needed to complete the missing types reaches up to 91.45% compared to the scenario where the language engineers had to identify and complete the types without guidance.     

A unified concurrent-composition method to state/event inference and concealment in labeled finite-state automata as discrete-event systems

Discrete-event systems (DESs) usually consist of discrete states and transitions between them caused by spontaneous occurrences of labeled events. In this review article, we study DESs modeled by labeled (nondeterministic) finite-state automata (LFSAs). Due to the partially-observed feature of DESs, fundamental properties therein can be classified into two categories: state/event-inference-based properties (e.g., strong detectability, diagnosability, and predictability) and state-concealment-based properties (e.g., opacity). Intuitively, the former category describe whether one can use observed output sequences to infer the current and subsequent states, past occurrences of faulty events, or future certain occurrences of faulty events; while the latter describe whether one cannot use observed output sequences to infer whether secret states have been visited (that is, whether the DES can conceal the status that its secret states have been visited). Over the past two decades these properties were studied separately using different methods, and particularly, in most works inference-based properties were verified based on two fundamental assumptions of deadlock-freeness and divergence-freeness, where the former implies that an automaton will always run, the latter implies that an automaton has no reachable unobservable cycle, hence the running of such an automaton will always be eventually observed. In this article, for LFSAs, a unified concurrent-composition method is shown to verify all above inference-based and concealment-based properties, resulting in a unified mathematical framework for the two categories of properties. In addition, compared with the previous methods in the literature, the concurrent-composition method does not depend on assumptions and is currently the most efficient. Finally, based on concurrent composition, we represent the negations of the above inference-based properties as linear temporal logic (LTL) formulae; by combining the concurrent composition and an additional tool called observer (i.e., the classical powerset construction for LFSAs), we also represent the above concealment-based properties as LTL formulae. Although LTL formulae model checking algorithms do not provide more efficient verification for these inference-based and concealment-based properties, the obtained LTL formulae show common similarities among these properties.     

Web-based distributed system and database modeling for concurrent design

This research introduces a new approach for Web-based collaborative concurrent design. In this approach, systems, product libraries, and product databases for modeling different product development life-cycle aspects are distributed at different locations that are linked through the Web. Product modeling libraries are described as class features. A class feature at a remote location can be used for defining a new class feature at the local site. Product modeling systems distributed at different locations are used for creating product databases that are described by instance features. A system at one location can be implemented using the functions provided at other locations as the components. Different life-cycle databases at different locations are associated by their relations. The optimal design considering relevant life-cycle aspects is identified using the distributed product life-cycle modeling systems and databases.     

Typed operational semantics for higher-order subtyping

Bounded operator abstraction is a language construct relevant to object oriented programming languages and to ML2000, the successor to Standard ML. In this paper, we introduce , a variant of F_<:^ω with this feature and with Cardelli and Wegner’s kernel Fun rule for quantifiers. We define a typed-operational semantics with subtyping and prove that it is equivalent with , using logical relations to prove soundness. The typed-operational semantics provides a powerful and uniform technique to study metatheoretic properties of , such as Church–Rosser, subject reduction, the admissibility of structural rules, and the equivalence with the algorithmic presentation of the system that performs weak-head reductions.Furthermore, we can show decidability of subtyping using the typed-operational semantics and its equivalence with the usual presentation. Hence, this paper demonstrates for the first time that logical relations can be used to show decidability of subtyping.     

对象系统的组合交互计算

对象系统的计算是一个开放的、动态并发交互的过程,由系统与外部环境的动态交互以及系统内部各组件间的协同工作来完成.对象系统的行为变化是系统内、外因有机统一的具体表征,因此不能把对象系统的静态组合构造和动态计算行为当作两个孤立的个体分而治之.从这个统一原则出发,研究了基于组合构造模型的对象系统的交互计算.组合构造模型设计将对象系统的主要计算特征纳入一个统一的抽象基调之中,通过定义基调上的一组关系,把对象系统的层次结构和内部协同工作有机地结合在一起.在此基础上,给出了一个区分动作类型的交互演算(S/R演算),描述了组合对象系统的动态行为和交互,较好地刻画出对象封装性、对象计算的事件驱动性、动态绑定以及对象系统内部的交互与并发等固有特征.     

A knowledge system for integrated product design

This paper discusses the architecture and implementation issues for a knowledge system to assist in product design. The goals of the concurrent Design Advisor (CODA) are to enhance the quality of designs by 25 percent and the efficiency by a factor of 10. The improvement springs from the integration of diverse knowledge bases, ranging from customer needs to product evaluation, and from process configuration to production control. One source of efficiency is the automation of many routine tasks, thereby increasing user productivity. Another source is the increase in the quality of initial designs, which obviates the need for numerous iterations in the design process due to poor manufacturability. CODA is based on the general architecture of the Creativity Support System, an expert system for assisting users in specific domains requiring creative solutions. The bilevel structure of the system consists of a domain-independent module containing general tools and techniques for creative problem-solving, and a domain-dependent module incorporating knowledge specific to particular fields of application. The utility of this approach is illustrated in the realm of concurrent product design by demonstrating a CODA within the general architecture of the system.     

Cooperative behavior acquisition for mobile robots in dynamically changing real worlds via vision-based reinforcement learning and development

In this paper, we first discuss the meaning of physical embodiment and the complexity of the environment in the context of multi-agent learning. We then propose a vision-based reinforcement learning method that acquires cooperative behaviors in a dynamic environment. We use the robot soccer game initiated by RoboCup (Kitano et al., 1997) to illustrate the effectiveness of our method. Each agent works with other team members to achieve a common goal against opponents. Our method estimates the relationships between a learner's behaviors and those of other agents in the environment through interactions (observations and actions) using a technique from system identification. In order to identify the model of each agent, Akaike's Information Criterion is applied to the results of Canonical Variate Analysis to clarify the relationship between the observed data in terms of actions and future observations. Next, reinforcement learning based on the estimated state vectors is performed to obtain the optimal behavior policy. The proposed method is applied to a soccer playing situation. The method successfully models a rolling ball and other moving agents and acquires the learner's behaviors. Computer simulations and real experiments are shown and a discussion is given.     

Hybrid client-server architecture and control techniques for collaborative product development using haptic interfaces

In this paper, a collaborative product development and prototyping framework is proposed by using distributed haptic interfaces along with deformable objects modeling. Collaborative Virtual Environment (CVE) is a promising technique for industrial product development and virtual prototyping. Network control problems such as network traffic and network delay in communication have greatly limited collaborative virtual environment applications. The problems become more difficult when high-update-rate haptic interfaces and computation intensive deformable objects modeling are integrated into CVEs for intuitive manipulation and enhanced realism. A hybrid network architecture is proposed to balance the computational burden of haptic rendering and deformable object simulation. Adaptive artificial time compensation is used to reduce the time discrepancy between the server and the client. Interpolation and extrapolation approaches are used to synchronize graphic and haptic data transmitted over the network. The proposed techniques can be used for collaborative product development, virtual assembly, remote product simulation and other collaborative virtual environments where both haptic interfaces and deformable object models are involved.     

Feature Based Modelling: A methodology for producing coherent,consistent, dynamically changing models of agents' competencies

Feature Based Modelling uses attribute value machine learning techniques to model an agent's competency. This is achieved by creating a model describing the relationships between the features of the agent's actions and of the contexts in which those actions are performed. This paper describes techniques that have been developed for creating these models and for extracting key information therefrom. An overview is provided of previous studies that have evaluated the application of Feature Based Modelling in a number of educational contexts including piano keyboard playing, the unification of Prolog terms and elementary subtraction. These studies have demonstrated that the approach is applicable to a wide spectrum of domains. Classroom use has demonstrated the low computational overheads of the technique. A new study of the application of the approach to modelling elementary subtraction skills is presented. The approach demonstrates accuracy in excess of 90% when predicting student solutions. It also demonstrates the ability to identify and model student's buggy arithmetic procedures.