摘要:

In this paper, an approach to the modelling and implementation of data-flow diagrams (DFDs) using Petri nets is introduced. A direction is identified where visualisation and high-level semantics can be incorporated into data-flow diagrams to facilitate direct manipulation, interpretation and validation. At the automation level, visualised DFDs generate layouts for data-flow vectors and use Petri nets to safeguard the correctness of a specification. The Petri net model uses a set of constraints to enforce consistency, both within and across diagrams. At the visual level, visualised DFDs replace the traditional textual specifications of the process and data-flow components with graphical forms. The entity-relationship model is adopted as the hierarchical and logical view of data.

DOI:10.1049/sej.1992.0001

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The futility of using a general-purpose metric to characterise ‘the’ complexity of a program has recently been argued to support the design of specific metrics for the different stages of the software life-cycle. An analysis of the module testing activity is performed, providing evidence of the absurdity of all-purpose metrics, as well as a methodical means with which to measuretestingcomplexity. Several standard metrics are seen to serve as component measures for the intricacies of testing. The methodology is applied to compare traditional and adaptive means of testing. It is shown that previous informal arguments asserting the superiority of adaptive methodologies are formally confirmed.

DOI:10.1049/sej.1992.0002

出版商:IEE    

年代:1992

数据来源: IET

摘要:

This paper describes a prototype user interface for a distributed software engineering environment, where the components of the environment are autonomous agents with some inherent decision-making capabilities. Agents may be distributed across a local-or wide-area network. Two forms of interaction are supported; namely, direct manipulation and message passing. Synchronous interaction is supported via the direct manipulation of system objects. Asynchronous interaction is managed by a central server agent, distributing electronic mail messages to the appropriate human or automated agents. The functionality of the system is illustrated by examples drawn from the domain of software development.

DOI:10.1049/sej.1992.0003

出版商:IEE    

年代:1992

数据来源: IET

摘要:

An interesting and little documented problem is the influence of a design methodology on the program architecture. In this case study, we compared two design methodologies and their impact on both development process and the resulting program architecture. The methodologies are object-based variants of refinement methodology and structured design, respectively. Both methodologies were applied to the same problem (a library system of less than 1000 lines of Ada code), and the results were compared. Substantial differences between the two resulting architectures are analysed and discussed.

DOI:10.1049/sej.1992.0004

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The all-du-paths structural testing criterion is one of the most discriminating of the data-flow testing criteria. Unfortunately, in the worst case, the criterion requires an intractable number of test cases. In a case study of an industrial software system, we find that the worst-case scenario is rare. Eighty percent of the subroutines require ten or fewer test cases. Only one subroutine out of 143 requires an intractable number of tests. However, the number of required test cases becomes tractable when using the all-uses criterion. This paper includes a formal specification of both the all-du-paths criterion and the software tools used to estimate a minimal number of test cases necessary to meet the criterion.

DOI:10.1049/sej.1992.0005

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The International Electrotechnical Commission is currently standardising four compatible languages for designing and implementing programmable logic controllers (PLCs). The language family includes a diagrammatic notation that supports the idea of software ICs to encourage graphical design techniques and systematic software reuse. This paper presents an interactive system with a graphical interface for constructing and validating PLC software. The semantics of a graphical design is defined by a mapping associating each design with an executable formal specification. The specification provides the basis for rigorous proofs and early tests of critical properties of a new design. A realistic example illustrates these features.

DOI:10.1049/sej.1992.0006

出版商:IEE    

年代:1992

数据来源: IET

摘要:

In this paper, we examine the design of a file system for a general-purpose scalable parallel computing engine, based on an extensible mesh of processors. Although many distributed file systems have already been developed, none have properly addressed the characteristics that are special to these computing engines, namely dynamic load-balancing and point-to-point networks. Client caching is identified as a key area where current systems fall short. We propose two new caching schemes that employ an extra level of caching in addition to that used by current client caching schemes. We present some results from a simulation study of the two new caching schemes, which demonstrate that the schemes outperform traditional client caching schemes when used in a general-purpose processor mesh-based, parallel computing engine. Since one of these caching schemes is quite complex, we have developed a formal specification in the Z language.

DOI:10.1049/sej.1992.0007

出版商:IEE    

年代:1992

数据来源: IET