Margaret Myers

A survey of current practice in the development of multimedia systems

Abstract A better understanding of the distinguishing characteristics of different forms of system development is vital if we are to tailor recommendations regarding good practice to the specific needs of particular projects. This paper presents the findings of a survey carried out in order to ascertain the current state of practice amongst developers of multimedia systems. The survey involved conducting structured interviews with professional multimedia developers from seven different organizations, and analysing feedback from postal questionnaires completed by developers working in 16 further organizations. The findings are used here to identify some of the features which distinguish multimedia system development projects from more conventional software developments.

Systems, models and measures

1.- 1 Introduction.- 2 Systems and Models.- 2.1 Intuitive notions.- 2.2 A systems approach to models.- 2.3 The system formed by the referent and its model.- 2.4 The two-part system: referent and environment.- 2.5 Black-box model: the referent as a unity.- 2.6 Structural model: the referent as a composition.- 2.7 Summary.- 2.8 References.- 3 Measures.- 3.1 Introduction.- 3.2 Characterizing a referent by measurement.- 3.3 Characterizing measures.- 3.4 Measurability.- 3.5 Metrology.- 3.6 Examples.- 3.7 Summary.- 3.8 References.- 4 Models of Specification and Design.- 4.1 Introduction.- 4.2 Products, processes, and the life history process.- 4.3 Specification of artefacts.- 4.4 Design of artefacts.- 4.5 Specification and design of processes.- 4.6 Summary.- 4.7 References.- 5 Measures of Specification and Design.- 5.1 Introduction.- 5.2 Measures and measurement schemes for product specifications.- 5.3 Process specification measures.- 5.4 FSP models and measures in practice.- 5.5 Summary.- 5.6 References.- 6 Constructing a Measurement Scheme.- 6.1 Introduction.- 6.2 Devising the case study demonstration.- 6.3 Measurement strategy options.- 6.4 A unifying reference language.- 6.5 Implementing a multiple-language strategy.- 6.6 The model-based measurement experiment.- 6.7 Summary and conclusions.- 6.8 References.- 2.- 7 A Formal Specification Medium.- 7.1 Introduction.- 7.2 Logic, Prolog and some specifications.- 7.3 Components of the Prolog logic text.- 7.4 The referent: the Prolog logic text.- 7.5 Language levels of formal specifications.- 7.6 Summary.- 7.7 References.- 8 Models and Measures of Structure.- 8.1 Introduction.- 8.2 Modelling the structure of Prolog logic text.- 8.3 Modelling programs.- 8.4 Measures of the structural model.- 8.5 The measurement tool SPA.- 8.6 Summary.- 8.7 References.- 9 Models and Measures of Data.- 9.1 Introduction.- 9.2 Models of the data of Prolog logic text.- 9.3 Measures of Prolog data.- 9.4 An example of measurement.- 9.5 The measurement scheme - a summary.- 9.6 References.- 10 An Experiment in Measuring Specifications.- 10.1 Introduction.- 10.2 Apparatus.- 10.3 Method.- 10.4 Results.- 10.5 Observations.- 10.6 Conclusions.- 10.7 References.- Appendix: Prolog code and measures of the specifications.

A first systems book : technology and management

Key Concepts Modelling Systems Measures Black Box Systems Structural Systems Products Processes: Product/Process Systems.

A Formal Specification Medium

To demonstrate the multiple-language measurement strategy described in Chapter 6, we must choose and use a reference language. Prolog has been shown to be suitable for the purpose, and although it is not our aim to teach the reader Prolog, we must explain its properties in just sufficient detail to demonstrate its role in the measurement strategy.

Models and Measures of Data

This chapter demonstrates a model-based measurement scheme at work on the data of the Prolog text. The abstraction of the logic component from the Prolog text is described in Section 7.3. Figure 7.6 shows that, for the purpose of modelling and measurement, the Prolog logic text divides into two parts: structure over data and the hierarchical structure of the logic text. This chapter is devoted to the former 0).

Systems and Models

The dictionary definition of ‘system’ is “a whole, composed of parts in orderly arrangement according to some scheme or plan”(1). This emphasizes two attributes: a system is a unity, and it is a composite. In accord with systems theory (see e.g.2,3,4), we regard ‘system’ as a generic notion which applies to any entity: concrete or abstract, natural or man-made, alive or inanimate. Any entity may be considered as a unity distinguished by the combination of its attributes, or as a composition of parts.

Models and Measures of Structure

The aim of this chapter is to present a model-based measurement scheme for characterizing the structure of Prolog logic texts. This chapter takes no account of the data content of the Prolog logic text, but concentrates only on the hierarchical relations in the structure, illustrated in figures 7.4a to 7.4c of Chapter 7.

An Experiment in Measuring Specifications

The aim of this chapter is to demonstrate the multiple-language strategy of model-based measurement outlined in Section 6.5. The material presented here is drawn from a comprehensive report (1), and sets out the assumptions and procedures of the case study. Of necessity, the treatment here is much curtailed. The aim of the experiment itself is to show to carry out model-bases measurement of formal and semi-formal specifications. The measurement proceeds in accord with the multiple-language strategy described in Figure 6.10.

Constructing a Measurement Scheme

Previously we demonstrated model-based measurement on simple examples, and discussed the notion of a model-based measurement scheme and its role in the validation of measures. We showed that a model-based measurement scheme is already implicit in mature disciplines whose models, theories and metrology are well established. The general applicability of model-based measurement indicates that one may also devise model-based measurement schemes for new fields of application, where such foundations are lacking.

Models of Specification and Design

In daily life, the terms ‘specification’ and ‘design’ are intuitively understood, and refer to other intuitive notions, such as ‘product’, ‘process’ and ‘artefact’. Through practice, these terms have acquired more precise meaning in the classical disciplines of engineering, but their casual usage still causes much uncertainty and confusion in many fields. Special concern arises in software- based systems which are increasingly entrusted with essential tasks in industry, finance, public administration and control of safety-sensitive plant. It is proving hard to specify and design such systems adequately, and to define for them standards which could assure their quality and safety.