Validation Of Formal Specifications Research Articles

Validation of formal specifications through transformation and animation

A significant impediment to the uptake of formal refinement-based methods among practitioners is the challenge of validating that the formal specifications of these methods capture the desired intents. Animation of specifications is widely recognized as an effective way of addressing such validation. However, animation tools are unable to directly execute (and thus animate) the typical uses of several of the specification constructs often found in ideal formal specifications. To address this problem, we have developed transformation heuristics that, starting with an ideal formal specification, guide its conversion into an animatable form. We show several of these heuristics and address the need to prove that the application of these transformations preserves the relevant behavior of the original specification. Portions of several case studies illustrate this approach.

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.

Facilitating formal specification acquisition by using recursive functions on context-free languages

Although formal specification techniques are very useful in software development, the acquisition of formal specifications is a difficult task. This paper presents the formal specification language LFC, which is designed to facilitate the acquisition and validation of formal specifications. LFC uses context-free languages for syntactic aspect and relies on a new kind of recursive functions, i.e. recursive functions on context-free languages, for semantic aspect of specifications. Construction and validation of LFC specifications are machine-aided. The basic ideas behind LFC, the main aspects of LFC, and the use of LFC and illustrative examples are described.

DECM, A User Oriented Formalism for High Level Discrete Event Specifications of Real-Time Systems

In this paper, we present DECM (Discrete Event Calculus Model), an original discrete event mathematical model for the specification of control systems at a high level of abstraction. Because the concept of event is more natural for nonspecialists than the concept of state, the proposed model is centered on the latter concept. This in turn permits the expression of asynchronous behavior without relying on the classical concept of state. In addition, DECM-based formalism offers an explicit representation of time that allows the use of timed simulations for the validation of formal specifications. This formalism is illustrated on a real-world industrial example.

Software development: two approaches to animation of Z specifications using prolog

Formal methods rely on the correctness of the formal requirements specification, but this correctness cannot be proved. This paper discusses the use of software tools to assist in the validation of formal specifications and advocates a system by which Z specifications may be animated as Prolog programs. Two Z/Prolog translation strategies are explored; formal program synthesis and structure simulation. The paper explains why the former proved to be unsuccessful and describes the techniques developed for implementing the latter approach, with the aid of case studies.