浅析JVM性能规范

Java语言有着独特的工作原理,这是由于Java引入的虚拟机(JVM)以及垃圾回收机制等功能所带来的.一切JavaEE应用都是基于JVM的,这些工作原理具体是如何工作,带来了怎样的便利,本文做出了比较详细的解答.     

Protective Interface Specifications

The interface specification of a procedure describes the procedure's behaviour using pre- and postconditions. These pre- and postconditions are written using various functions. If some of these functions are partial, or underspecified, then the procedure specification may not be well-defined. We show how to write pre- and postcondition specifications that avoid such problems, by having the precondition “protect” the postcondition from the effects of partiality and underspecification. We formalize the notion of protection from partiality in the context of specification languages like VDM-SL and COLD-K. We also formalize the notion of protection from underspecification for the Larch family of specification languages, and for Larch show how one can prove that a procedure specification is protected from the effects of underspecification. Received October 1997 / Accepted in revised form March 1998     

XML的标准规范

本文首先介绍了XML的结构和特点,以及XML的相关技术规范标准,然后结合XML和数据库的优缺点,讨论了基于XML的数据库中间件技术.     

Presheaves as Configured Specifications

The paper addresses a notion of configuring systems, constructing them from specified component parts with specified sharing. This notion is independent of any underlying specification language and has been abstractly identified with the taking of colimits in category theory. Mathematically it is known that these can be expressed by presheaves and the present paper applies this idea to configuration. We interpret the category theory informally as follows. Suppose ? is a category whose objects are interpreted as specifications, and for which each morphism u : X→Y is interpreted as contravariant ‘instance reduction’, reducing instances of specification Y to instances of X. Then a presheaf P: Set ^?op represents a collection of instances that is closed under reduction. We develop an algebraic account of presheaves in which we present configurations by generators (for components) and relations (for shared reducts), and we outline a proposed configuration language based on the techniques. Oriat uses diagrams to express colimits of specifications, and we show that Oriat's category Diag(?) of finite diagrams is equivalent to the category of finitely presented presheaves over ?. Received May 1998 / Accepted in revised form August 2000     

Model Checking Interactor Specifications

Recent accounts of accidents draw attention to “automation surprises” that arise in safety critical systems. An automation surprise can occur when a system behaves differently from the expectations of the operator. Interface mode changes are one class of such surprises that have significant impact on the safety of a dynamic interactive system. They may take place implicitly as a result of other system action. Formal specifications of interactive systems provide an opportunity to analyse problems that arise in such systems. In this paper we consider the role that an interactor based specification has as a partial model of an interactive system so that mode consequences can be checked early in the design process. We show how interactor specifications can be translated into the SMV model checker input language and how we can use such specifications in conjunction with the model checker to analyse potential for mode confusion in a realistic case. Our final aim is to develop a general purpose methodology for the automated analysis of interactive systems. This verification process can be useful in raising questions that have to be addressed in a broader context of analysis.     

Architectural Specifications in CASL

One of the most novel features of CASL, the Common Algebraic Specification Language, is the provision of so-called architectural specifications for describing the modular structure of software systems. A brief discussion of refinement of CASL specifications provides the setting for a presentation of the rationale behind architectural specifications. This is followed by some details of the features provided in CASL for architectural specifications, hints concerning their semantics, and simple results justifying their usefulness in the development process. Received October 2000 / Accepted in revised form July 2001     

Safe Data Type Specifications

This paper discusses the current style of algebraic data type specifications. Some simple examples illustrate that whether or not two objects of the type being specified are equal can be implementation dependent, even for very simple objects of the type. To remedy this, it is proposed that specifications should be safe, where safety is a stronger requirement than Guttag's sufficient completeness. The paper also discusses when an operator should be part of a specification and when it should be introduced by extension, and concludes with safe specifications of some common data types.     

Specifications of distributed programs

This paper discusses informal specifications of distributed programs, that is, programs that reside at nodes connected by a network. Such programs often have performance requirements, such as high availability and concurrency, that make it difficult to specify their behavior. These requirements often have an effect on the functional behavior of a program, forcing designers to change their initial expectations. In this paper we show how to give user-oriented specifications of the functional behavior of programs with such requirements. We propose a structure for specifications that distinguishes expected and desirable effects from undesirable ones. We believe that this distinction is an important one for both users and implementers of a system, and that it makes the specifications easier to understand. We illustrate our approach by giving example specifications of several distributed programs that have been described in the literature.     

On Formalism in Specifications

A critique of a natural-language specification, followed by presentation of a mathematical alternative, demonstrates the weakness of natural language and the strength of formalism in requirements specifications.     

Specifications for decidable hybrid games

We introduce STORMED hybrid games (SHG), a generalization of STORMED hybrid systems, Vladimerou et al. (2008) [33], which have natural specifications that allow rich continuous dynamics and various decidable properties. We solve the control problem for SHG using a reduction to bisimulation on finite game graphs. This generalizes to a greater family of games, which includes o-minimal hybrid games, Bouyer et al. (2006) [6]. We also solve the optimal-cost reachability problem for Weighted SHG and prove decidability of WCTL for Weighted STORMED hybrid systems.     

Patterns for Timed Property Specifications

Patterns for property specification enable non-experts to write formal specifications that can be used for automatic model checking. The existing patterns identified in [Dwyer, M.B., G.S. Avrunin and J.C. Corbett, Property specification patterns for finite-state verification, in: FMSP '98: Proceedings of the second workshop on Formal methods in software practice (1998), pp. 7–15] allow to reason about occurrence and order of events, but not about their timing. We extend this pattern system by patterns related to time. This allows the specification of real-time requirements.     

拓展Play—FiTM无线音频技术

高清音频解决方案者DTS,Inc．将其Play—FiTM无线平台拓展到中国。拓展进该市场的同时,中国音乐服务提供商QQ音乐（QQMusic）如今被无缝整合进Play—Fi应用。     

Component Specifications for Robotics Integration

Robotics researchers have been unable to capitalize easily on existing software components to speed up their development efforts and maximize their system's capabilities. A component-based approach for building the software for robotics systems can provide reuse and sharing abilities to the research community. The software engineering community has been studying reuse techniques for three decades. We present several results from those efforts that are applicable to the robotics software integration problem. We describe how to specify a software component so that a potential user may understand its capabilities and facilitate its application to his or her system. At the National Institute of Standards and Technology, we have developed a three-stage, component-specification approach. We illustrate this approach for a component that is relevant to robotics.     

Separate Compilation of Polychronous Specifications

As code generation for synchronous programs requires strong safety properties to be satisfied, compositionality becomes a difficult goal to achieve. Most synchronous languages, such as Esterel, Lustre or Signal require a given module or compilation unit to be insensitive to latency that communication with its environment may incur. In Lustre or Signal, for instance, a compilation unit must satisfy the so-called property of endochrony. To preserve endochrony in an asynchronous environment, an ad-hoc protocol is synthesized to interface the module. However, endochrony is not preserved by composition. Consequently, the protocol has to be rebuilt every time a new module is added in the environment. We propose a methodology and code generation scheme which simplifies this concern. It consists of weakening the global objective of globally preserving endochrony. Instead, we aim at the preservation of a more liberal and compositional objective, weak endochrony [D. Potop-Butucaru and B. Caillaud and A. Benveniste. Concurrency in Synchronous Systems. In Formal Methods in System Design, v. 28(2). Springer, March 2006], which is compositional and much closer from the expected requirement of insensitivity to communication latency. As a result, our code generation scheme supports true separate compilation: a locally compiled synchronous module does not require its synthesized interface with the environment to be rebuilt once composed with another module.     

Refinement-based Validation of Event-B Specifications

The validation of formal specifications is a challenging task. It is one of the factors that impede the penetration of formal methods into the common practices of software development. This paper discusses the issue of validating formal models by executing them in the context of Event-B. The most important problem lies in the non-determinism which often prevents purely automatic tools to execute models. In this paper, we first present and discuss the techniques we have created to allow the execution of models at all levels of abstraction. These techniques rely on users to overcome the barriers resulting from non-deterministic features by either modifying the model or providing ad hoc implementations. Then, we present our main contribution, the formal definition of the notion of fidelity, that guarantees that all the observable behaviors of the executable models are indeed specified by the original (non-deterministic) models. The notion of fidelity can be expressed in terms of proof obligations.