Model-based Specification Language Research Articles

Object-oriented model-based specification languages

Complex, soft-real-time system development is one of the challenges in the software industry, as it is difficult to understand, test and maintain such systems. However, the software development goal is to operate reliably despite this complexity. This can be achieved by applying formal methods, which use a language that has a strong mathematical foundation for describing the system. To be more specific, model-based specification languages are used to resolve ambiguities in user requirements or detect design errors early in the software life cycle. This paper compares object-oriented model-based formal languages such as Zed (Z), Vienna Development Method (VDM) and Object Constraint Language (OCL) based on various factors. Also, the issues surrounding the application of these formal methods to various software problems are discussed in this paper. The present research work enables software developers to select an appropriate language suiting their specific requirements.

SLABS: A FORMAL SPECIFICATION LANGUAGE FOR AGENT-BASED SYSTEMS

Being autonomous, proactive and adaptive, an agent-based system may demonstrate emergent behaviours, which are neither designed by the developers nor expected by the users of the system. Whether or not such emergent behaviours are advantageous, methods for the specification of agent behaviours must be developed to enable software engineers to analyse agent-based systems before they are implemented. This paper presents a formal specification language SLABS for agent-based systems. It is a model-based specification language defined based on the notion of agents as encapsulations of data, operations and behaviours. The behaviour of an agent is defined by a set of rules that describe the action/reaction of the agent in certain environment scenarios. The style and expressiveness of the language is demonstrated by examples like ants, personal assistants and speech-act style of agent communications.

A toolset to support the construction and animation of formal specifications

Model-based specification languages, in particular Z, have been widely used to provide a precise and unambiguous statement of the proposed system as perceived by the developer. However, for many complex specifications, developers cannot themselves be sure about the “intended behaviour” of the specification constructed. This paper reports on an approach and toolset that enables a developer to construct a Z specification using the wiZe editor, demonstrate its properties by transforming it into an executable form using the ZAL animation system, and explore its adequacy by animating a variety of scenarios. The application of the approach and toolset is demonstrated on a specification of a telephone network to illustrate that specification validation could be carried out incrementally during development through investigative scenarios to assess the adequacy of the specification. It is claimed that this interaction, when used in peer review or by the individual developer, can provide enhanced accessibility, a better understood and possibly an improved specification.

Specification and Animation of a Bank Transfer using KIDS/VDM

The development of formal specifications may benefit from prototyping activities. The production of an executable model for a given description helps bridging the gap between this specification and the corresponding reality. The KIDS/VDM system, based on the KIDS environment, provides these prototyping facilities for the model-based specification language of VDM. This paper illustrates its use in the specification of a bank transfer operation. The specification process starts from an abstract specification and details it by a series of refinements of either the control flow or the data structures. The case study shows how animation may be helpful at several stages of the process. It favours the dialog between the specifier and his customer and helps assessing the correspondence between the description and the actual problem. It also convinces the specifier of the validity of his refinements before he fulfills the necessary proof obligations.

A language-independent approach to specification construction

An interactive specification development environment is presented in which a number of development methodologies and specification languages can be supported. Within the environment, design concepts and strategies are captured by the application of development operators , i.e. operators which enable the incremental construction and modification of specifications.The focus of this paper is to investigate the language independence feature of the environment, based on the work done in the Esprit project ICARUS. A set of operators enabling an object-oriented approach to specification development are instantiated for both the algebraic specification language Glider and the model-based specification language Z. These operators are illustrated by the development of a case study of a simple card game in both Glider and Z.

Refinement methods and refinement calculi

A number of modern approaches to refinement are discussed and compared, and their broad classification into refinement methods and refinement calculi is explained. The refinement methods concerned are all based on the model-based specification languages VDM and Z, whereas the refinement calculi are all developments of the Dijkstra programming calculus. A generalised comparison of the refinement methods and the refinement calculi is also given.