Translating VDM specifications into ABC programs

Declarative languages such as Miranda and Prolog have often been used to prototype specifications written in the formal notation of VDM, but they have no destructive assignment commands thus making it difficult to model VDM state changes. Imperative languages like C and Pascal allow state changes to be modelled naturally but lack the expressive power to make prototyping feasible. ABC, on the other hand, is a simple yet very powerful imperative language that has a great expressive power making it suitable as a prototyping language. This paper describes the process of translating VDM specifications into ABC programs.     

基于数据分解的并发面向对象程序开发方法

提出了一种从VDM-SL(Vienna development method-specification language)规约到并发面向对象程序的开发方法,这种方法基于DD-VDM(data decomposition-Vienna development method).在此基础上提出了虚拟原子、服务并行和内部并行等概念,继而提出一种嵌套面向对象结构来体现这些功能.分别从共享量并行系统和分布并行系统的角度讨论了嵌套面向对象结构的实现技术.     

A System for Translating Executable VDM Specifications into Lazy ML

This article describes the process of developing a system for translating VDM executable specifications into Lazy ML prototypes. The system was specified in VDM and a Lazy ML prototype implementation was derived from its specification. This article concentrates on discussing the lessons learned in each stage of the development process, evaluating the adequacy of the used methodology. © 1997 by John Wiley & Sons, Ltd.     

A Formal Semantics of Data Flow Diagrams

This paper presents a formal semantics of data flow diagrams as used in Structured Analysis, based on an abstract model for data flow transformations. The semantics consists of a collection of VDM functions, transforming an abstract syntax representation of a data flow diagram into an abstract syntax representation of a VDM specification. Since this transformation is executable, it becomes possible to provide a software analyst/designer with two ‘views’ of the system being modelled: a graphical view in terms of a data flow diagram, and a textual view in terms of a VDM specification. In this paper emphasis is on the motivation for the choices made in the transformation. The main aspects of the transformation itself are described using annotated VDM functions with some examples.     

A safe regression testing approach for safety critical systems

Regression testing is important activity during the software maintenance to deal with adverse effects of changes. Our approach is important for safety critical system as usually formal methods are preferred and highly recommended for the safety critical systems but they are also applied for the systems development of other than critical system. Our approach is based on Regression testing using VDM++ which takes two VDM++ specifications, one baseline and other delta (Changed) along with test suite for the baseline version. It compares both versions by using comparator module, identifies the change. By analyzing the change we classify the test cases from original test suite into obsolete, re-testable, and reusable test cases. Our scope is at unit level i.e. at class level. Our approach gets two versions of VDM++ specification and returns regression test suite for the delta version. Our approach distinguishes test cases which are still effective for the delta version of VDM++ specification and it differs from re-test all strategy as it can distinguish the test cases and identifies test cases which are useful for delta version. Test cases reusability and test case reduction is the main objective of our approach. Our approach presents how to perform regression testing using VDM++ specification during the maintenance of systems.     

Informal and formal requirements specification languages: bridgingthe gap

The differences between informal and formal requirements specification languages are noted, and the issue of bridging the gap between them is discussed. Using structured analysis (SA) and the Vienna development method (VDM) as surrogates for informal and formal languages, respectively, two approaches are presented for integrating the two. The first approach uses the SA model of a system to guide the analyst's understanding of the system and the development of the VDM specifications. The second approach proposes a rule-based method for generating VDM specifications from a set of corresponding SA specifications. The two approaches are illustrated through a simplified payroll system case. The issues that emerge from the use of the two approaches are reported     

Searching for a Global Search Algorithm

We report on a case study to assess the use of an advanced knowledge-based software design technique with programmers who have not participated in the technique's development. We use the KIDS approach to algorithm design to construct two global search algorithms that route baggage through a transportation net. Construction of the second algorithm involves extending the KIDS knowledge base. Experience with the case study leads us to integrate the approach with the spiral and prototyping models of software engineering, and to discuss ways to deal with incomplete design knowledge.     

A VDM case study in mural

The application of an interactive theorem-proving assistant and specification support tool called mural in the specification and verification of a small Vienna development method (VDM) development is described. It is the authors' intention to give a feel for how mural works and of mural's applicability as a tool in specifying and verifying software     

VDM和Z两种规范描述语言的比较

本文以以关系数据库的规范为例，详细讨论了两种重要的规范描述语言ＶＤＭ和Ｚ的主要区别，对它们的共性和发展史也作了简单介绍。     

Dealing with different time granularities in formal specifications of real-time systems

The article presents a formalization of the notion of time granularity within a logical language for specifying real-time systems. It provides the specifier with the ability of dealing with different time granularities within a single specification. That is, it allows the specifier to describe the behavior and the properties of a system and its environment with respect to different time scales and to switch among them in a suitable way. The extended logical formalism is then embedded in an object oriented structure that enhances both the expressive power and the executability of the specification language. With regard to expressiveness, it enables one to subdivide a single specification of the system and its environment into different part and to provide a number of specifications of them at different levels of abstraction, each one referring to a different time granularity. With regard to executability, it allows one to verify the consistency and the adequacy of specifications at each step of their incremental development. It also suggests an enlargement of the notions of verification and validation that takes into account the stratified structure of the object oriented specifications.     

Temporal-logic property preservation under Z refinement

Formal specification languages such as Z, B and VDM are used in the incremental development of abstract specifications (suitable for establishing required properties) to more concrete specifications (resembling the final implementation). This incremental development process, known as refinement, preserves all observable properties of the original abstract specification. Recent research has looked at applying temporal-logic model checking to such specification languages. While this assists in the establishment of properties of the abstract specification, temporal-logic properties typically refer to state variables which are regarded as non-observable. Hence, such properties are not guaranteed to be preserved by refinement. This paper investigates the classes of temporal-logic properties which are preserved by refinement, and for some of those properties that are not preserved in general, the restrictions on the refinement process under which they are preserved. Results are presented for the temporal logics LTL, CTL and the μ-calculus and the formal specification language Z. They apply equally, however, to related formal specification languages such as B and VDM.     

A Method for Extracting and Stating Software Requirements that a User Interface Prototype Contains

User interface and requirements prototyping is a requirements elicitation technique. A user interface and requirements prototype is built during the requirements engineering phase of a software system development. Along with the user interface prototype are produced various documents such as the system requirement specification. When a prototype and other documents exist, they may not describe the same functionality, particularly because there may be behaviour of the prototype, artefacts of prototyping, that may not be intended. The problem is that in later development stages, when there is a prototype and other documents, it is often difficult to reconcile the difference between the prototype and the other documents. This paper presents an approach for avoiding this difficulty. It demonstrates the approach by showing its application to parts of a real software development.     

实时视景仿真技术在疏浚仿真训练器中的应用

该文详细介绍了成功运用美国Multigen-Paradigm公司的MultiGen Creator和Vega软件实现1750疏浚仿真训练器的虚拟视景的方法。Vega是一个用于虚拟现实和实时仿真应用的软件环境,支持复杂视景仿真的快速原型开发。MultiGen Creator是一个基于X WindowsTM用户界面的三维图形编辑器。上述工具使用户可以快速地在一个所见即所得的环境中创建和修改视景数据库。在培训过程中,视景仿真子系统接受控制盘台发出的指令,使虚拟场景中的挖泥船各运动部件可随操作手柄同步运动,帮助学员观测其操作的正确性,同时让学员有身临其境的感觉。