A user-friendly formal requirements specification method

A user-friendly formal requirements specification method -...

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A User-Friendly Formal Requirements Specification Method Shaoying Liu University of York England Abstract As formal methods are increasingly used in the development of industrial scale software systems, there is a growing awareness of the need to in- tegrate the formal notations with existing struc- tured software development methods. In order to make requirements analysis both comprehensible and rigorous, a User-Friendly Formal Requirements Specification Method is proposed in this paper by combining and extending DeMarco data flow dia- grams with VDM (Vienna Development Method). The specifications produced using this method pos- sess good readability, a well-designed structuring mechanism and precise semantics. The significant progress presented in this paper is to develop a veri- fied analysis approach based on the concept of con- sistency checking for guaranteeing the correctness of analysis steps. Keywords: Requirements analysis, Formal require- ments specification, Consistency analysis, Formal methods. 1 Introduction The development of any large system must be pre- ceded by the construction of a specification of what is required. Without such a specification, the peo- ple charged with development will have no firm idea of the needs of the would-be users of the system. The DeMarco data flow diagram, DDFD for short, is the most popular informal structured specifica- tion construction tool [1][2][3] as it has created an approach by which a developer and someone outside the field can communicate. It has a graphic repre* sentation with only a few primitives and concepts. Pennlssion to copy without fee all of part oi r this material is 8ranted provided that the copies are not made c~ di~ib~ed for direct commercial advantage, the ACM copyright notice and the title d the publication and i~ date appear, and notice is given that copyi~ is by pmmi~ico of the AJumciation for Compul~ng Machinery. To copy otherwise, of to republ~h, n~qulzof • fee and/of ~%~'~c pem~.io~ A complex system specification can be decomposed into a modular and hierarchical structure which is very comprehensible. However, requirements ex- pressed using DDFD may be ambiguous, and the model lacks the formality to provide a specification for rigorous development. As the formal method VDM [4][5] is increasingly used in the development of industrial scale soft- ware systems [6][7], there is a growing awareness of the need to integrate VDM and the model of Data Flow Digram in order to achieve the formalisation of this model. Fraser [8] bridges the gap between informal and formal requirements analysis by using Data Flow Diagram and VDM sequentially, but this does not make contribution to the formalisation of the model of Data Flow Diagram. Liu [9] provides a formal structured requirements analysis method by combining DeMarco Data Flow Diagram with VDM. The precise semantics of a requirement spec- ification created by using this method is defined, and the correctness proof of specifications are ad- dressed. However, there are two deficiencies in Liu's
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A user-friendly formal requirements specification method -...

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