Hardware and software systems will inevitably grow in scale and functionality. Because of this increase in complexity, the likelihood of subtle errors is much greater. Moreover, some of these errors may cause catastrophic loss of money, time, or even human life. A major goal of software engineering is to enable developers to construct systems that operate reliably despite this complexity. One way of achieving this goal is by using formal methods, which are mathematically based languages, techniques, and tools for specifying and verifying such systems. Use of formal methods does not a priori guarantee correctness. However, they can greatly increase our understanding of a system by revealing inconsistencies, ambiguities, and incompleteness that might otherwise go undetected. The first part of this report assesses the state of the art in specification and verification. For verification, we highlight advances in model checking and theorem proving. In the three sections on specification, model checking, and theorem proving, we explain what we mean by the general technique and briefly describe some successful case studies and well-known tools. The second part of this report outlines future directions in fundamental concepts, new methods and tools, integration of methods, and education and technology transfer. We close with summary remarks and pointers to resources for more information.

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Formal methods: state of the art and future directions

Formal methods used in developing computer systems (i.e. mathematically based techniques for describing system properties) are defined, and their role is delineated. Formal specification languages, which provide the formal method's mathematical basis, are examined. Certain pragmatic concerns about formal methods and their users, uses, and characteristics are discussed. Six well-known or commonly used formal methods are illustrated by simple examples. They are Z, VDM, Larch, temporal logic, CSP, and transition axioms. >

A specifier's introduction to formal methods

Behavioral interface specification languages provide formal code-level annotations, such as preconditions, postconditions, invariants, and assertions that allow programmers to express the intended behavior of program modules. Such specifications are useful for precisely documenting program behavior, for guiding implementation, and for facilitating agreement between teams of programmers in modular development of software. When used in conjunction with automated analysis and program verification tools, such specifications can support detection of common code vulnerabilities, capture of light-weight application-specific semantic properties, generation of test cases and test oracles, and full formal program verification. This article surveys behavioral interface specification languages with a focus toward automatic program verification and with a view towards aiding the Verified Software Initiative—a fifteen-year, cooperative, international project directed at the scientific challenges of large-scale software verification.

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Behavioral interface specification languages

This paper presents a method of formally specifying concurrent systems which uses the object-oriented state-based specification language Object-Z together with the process algebra CSP Object-Z provides a convenient way of modelling complex data structures needed to define the component processes of such systems, and CSP enables the concise specification of process interactions The basis of the integration is a semantics of Object-Z classes identical to that of CSP processes This allows classes specified in Object-Z to be used directly within the CSP part of the specification

A Semantic Integration of Object-Z and CSP for the Specification of Concurrent Systems

The formal development of large or complex systems can often be facilitated by the use of more than one formal specification language Such a combination of languages is particularly suited to the specification of concurrent or distributed systems, where both the modelling of processes and state is necessary This paper presents an approach to refinement and verification of specifications written using a combination of Object-Z and CSP (communicating sequential processes) A common semantic basis for the two languages enables a unified method of refinement to be used, based upon CSP refinement To enable state-based techniques to be used for the Object-Z components of a specification, we develop state-based refinement relations which are sound and complete with respect to CSP refinement In addition, a verification method for static and dynamic properties is presented The method allows us to verify properties of the CSP system specification in terms of its component Object-Z classes by using the laws of the CSP operators together with the logic for Object-Z

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Refinement and verification of concurrent systems specified in Object-Z and CSP

This paper presents the RAISE1 software development method, its associated specification language, and the tools supporting it. The RAISE method enables the stepwise development of both sequential and concurrent software from abstract specification through design to implementation. All stages of RAISE software development are expressed in the wide-spectrum RAISE specification language. The RAISE tools form an integrated tool environment supporting both language and method.

The paper surveys RAISE and furthermore, more detailed presentations of major RAISE results are provided. The subjects of these are (a) an example of the use of the RAISE method and language, and (b) a presentation of the mathematical semantics of the RAISE specification language.

The RAISE language, methods and tools

This paper presents the RAISE software development method, its associated specification language, and the tools supporting it. The RAISE Method enables the stepwise development of both sequential and concurrent software from abstract specification through design to implementation. All stages of RAISE software development are expressed in the wide-spectrum RAISE Specification Language. The RAISE Tools forms an integrated tool environment supporting both language and method.

Klaus Havelund

Papers

The RAISE language, methods and tools

The RAISE language, method and tools