Counterexamples to applicative simulation and extensionality in non-deterministic call-by-need lambda-calculi with letrec

This note provides an example that demonstrates that in non-deterministic call-by-need lambda-calculi extended with cyclic let, extensionality as well as applicative bisimulation in general may not be used as criteria for contextual equivalence w.r.t. may- and two different forms of must-convergence. We also outline how the counterexample can be adapted to other calculi.     

Efficient weakest preconditions

Desired computer-program properties can be described by logical formulas called verification conditions. Different mathematically-equivalent forms of these verification conditions can have a great impact on the performance of an automatic theorem prover that tries to discharge them. This paper presents a simple weakest-precondition understanding of the ESC/Java technique for generating verification conditions. This new understanding of the technique spotlights the program property that makes the technique work.     

Verifying lossy channel systems has nonprimitive recursive complexity

Lossy channel systems are systems of finite state automata that communicate via unreliable unbounded fifo channels. It is known that reachability, termination and a few other verification problems are decidable for these systems. In this article we show that these problems cannot be solved in primitive recursive time.     

Using a process algebra interface for verification and validation of UML statecharts

UML diagrams are the conventional methods for visual modeling systems. Among them, the Statechart diagrams are used to show the runtime behavior of a system, but the correctness of such diagrams is the primary concern of the designers because of concurrency issues like livelock, inaccessible states, and non-deterministic states. Process algebra methods have the capabilities that are suitable for verification and validation of Statecharts. To this end, in this paper, process algebra language LOTOS (Language Of Temporal Ordering Specification) is used as the target language, and a method is presented to map UML Statecharts to the LOTOS processes, called USLP. Then the correctness of the proposed mappings is proved by demonstrating the isomorphism relation between the Labeled Transition System (LTS) of a Statechart and the LTS of its transformed LOTOS specification. Next, tools CADP (Construction and Analysis of Distributed Processes) is used for verification and validation of the mapped LOTOS models, and the CSP process algebra and its tools, FDR are used to verify the properties could not be verified by the LOTOS and its toolset. The experimental results show our approach can: (1) verify some properties (the issues) that are not verified by other approaches and (2) reduce the space that should be searched to verify the properties.     

Two implementations of the Ada program library

The programming language Ada defines a separate compilation mechanism which must enforce the language rules in the same manner when compiling a program either in several units or as one compilation unit. Two implementations of the Ada program library required by this mechanism are described. Each has an associated compiler manager program which is the user's interface to the library. The first maintains a central map file containing the library structure. The second uses the UNIX tool make to maintain the library and permits more flexibility in the UNIX operating system environment. Higher level tools could use the second manager as a component part.     

Soundness in verification of algebraic specifications with OBJ

The algebraic specification tools of the OBJ family have no notion of open terms or quantifiers. Nonetheless there are methods of proving universally quantified statements about specifications. These methods are examined and found to be unsound.     

Propositional dynamic logic of context-free programs and fixpoint logic with chop

This paper compares propositional dynamic logic of non-regular programs and fixpoint logic with chop. It identifies a fragment of the latter which is equi-expressive to the former. This relationship transfers several decidability and complexity results between the two logics.     

Use of a formal notation for static semantics in compiler design

Formal notations for the specification of the syntax and the dynamic semantics of languages exist and are of great benefit to the compiler writer. However, formal notations for the static semantics of languages have tended to be tools of the language designer and of little practical significance to the compiler writer. This paper describes how a particular notation was used to assist in the implementation of a Cobol compiler and of an interpreter for a simulation language.     

A residualizing semantics for the partial evaluation of functional logic programs

Recent proposals for multi-paradigm declarative programming combine the most important features of functional, logic and concurrent programming into a single framework. The operational semantics of these languages is usually based on a combination of narrowing and residuation. In this paper, we introduce a non-standard, residualizing semantics for multi-paradigm declarative programs and prove its equivalence with a standard operational semantics. Our residualizing semantics is particularly relevant within the area of program transformation where it is useful, e.g., to perform computations during partial evaluation. Thus, the proof of equivalence is a crucial result to demonstrate the correctness of (existing) partial evaluation schemes.     

Object-Z: A specification language advocated for the description of standards

The importance of formalising the specification of standards has been recognised for a number of years. This paper advocates the use of the formal specification language Object-Z in the definition of standards. Object-Z is an extension to the Z language specifically to facilitate specification in an object-oriented style. First, the syntax and semantics of Object-Z are described informally. Then the use of Object-Z in formalising standards is demonstrated by presenting a case study based on the ODP Trader. Finally, a formal semantics is introduced that suggests an approach to the standardisation of Object-Z itself. Because standards are typically large complex systems, the extra structuring afforded by the Object-Z class construct and operation expressions enables the various hierarchical relationships and the communication between objects in a system to be succinctly specified.     

Integrating predicate transition nets with first order temporal logic in the specification and verification of concurrent systems

This paper presents some results of integrating predicate transition nets with first order temporal logic in the specification and verification of concurrent systems. The intention of this research is to use predicate transition nets as a specification method and to use first order temporal logic as a verification method so that their strengths — the easy comprehension of predicate transition nets and the reasoning power of first order temporal logic can be combined. In this paper, a theoretical relationship between the computation models of these two formalisms is presented; an algorithm for systematically translating a predicate transition net into a corresponding temporal logic system is outlined; and a special temporal refutation proof technique is proposed and illustrated in verifying various concurrent properties of the predicate transition net specification of the five dining philosophers problem.     

Web交互模型的形式化验证研究

Web交互模型的形式化验证是对Web事件属性进行校验的十分可信的方法。通过一系列的系统模型建立、系统行为分析以及对于模型中关心属性的相关验证,能够让交互模型在设计阶段就能使形式化模型暴露出其所存在的缺陷,而不至于让缺陷保留到编码阶段或者更后面才能被真正地暴露出来,这样使系统模型的生存能力更加强大,同时避免了因后期缺陷暴露而出现的大代价修复。通过对Web系统的交互应用服务的过程模型化的体系进行研究,通过模型本身具有的属性进行相关正确性的校验,主要通过使用数学推理实现系统逻辑上的服务交互进程,从而进行过程的推演,并对系统服务的正确性进行过程的形式化验证,从而使系统服务模块的属性正确性可以通过逻辑上的演进来发现服务问题的存在,而不再是系统通过编码实现后才发现。对Web交互模型的形式化验证是基于IMWSC模型语义形成的IMWSC模型的验证机制。     

Generalised multi-pattern-based verification of programs with linear linked structures

The paper deals with the problem of automatic verification of programs working with extended linear linked dynamic data structures, in particular, pattern-based verification is considered. In this approach, one can abstract memory configurations by abstracting away the exact number of adjacent occurrences of certain memory patterns. With respect to the previous work on the subject the method presented in the paper has been extended to be able to handle multiple patterns, which allows for verification of programs working with more types of structures and/or with structures with irregular shapes. The experimental results obtained from a prototype implementation of the method show that the method is very competitive and offers a big potential for future extensions.     

Design and formal proof of a new optimal image segmentation program with hypermaps

This article presents the design of a new functional 2D image segmentation algorithm by cell merging in a subdivision, its proof of total correctness, and the derivation of an optimal imperative program. The planar subdivisions are modeled by hypermaps. The formal specifications of hypermaps and segmentation are developed in the Calculus of Inductive Constructions. The proofs are assisted by the Coq system. The final program is written in C.     

Ada语言的发展

Ada语言诞生于1979年,1980年被指定为美国军用标准,1983年被正式确立为ISO标准并投入使用。Ada所追求的主要目标是:程序的可靠性与可维护性、程序设计作为人的活动(强调程序可读性比可写性更重要)以及效率。Ada凭借其强大的功能、良好的可靠性以及对软件工程思想的优良体现在20世纪最后20年对程序设计语言的发展产生了重要影响。Ada广泛应用于高可靠、长生存期的大型软件研发,在军事、商业、公共交通、金融等领域的核心软件开发中发挥着重要作用。诸多欧美国家的国防与空中管制系统、交通运输系统、银行安全防卫系统等均使用Ada语言研制开发。迄今为止,国际标准组织先后确立过Ada 83,Ada 95,Ada 2005,Ada 2012等4个语言标准,新标准在旧标准的基础上均保持了良好的兼容性。从语言机制、应用、影响力等方面对Ada语言的发展进行全面的介绍和分析。