Methods and tools for information systems design

Abstract

The purpose of this survey is to present, in a comprehensive manner, some important concepts that influenced th~ design of information systems in the last few years. Emphasis is placed on recent progress in design methods, and on the development of tools that may be used to apply these methods.Some aspects of recent computer-implemented systems for assistance to req~airements analysis and system design are examined. The paper then reviews some advances in the design of data and control structures. The impact of the abstract data type concept and its use in system design is analyzed. Recent progress in the control of parallel process cooperation is finally presented, with reference to distributed systems. i. -ARCHITECTURAL PRINCIPLESA system may be defined, in general terms, as a set of interacting components. In a man-made (as opposed to natural) system, these components are designed to oper~e together towards some defined objective or purpose. A component of a system may be an elementary object, or a system in itself (in which case it is called a subsystem).Information processing is a global term for the set of operations (input, output, transmission, storage, retrieval, transformation,..) that may be applied to da~ m.The purpose of an information system is to provide a support for a variety of information processing tasks (technical, clerical or managerial) that are required by an organization. Such a system is not closed, i.e. it interacts with an environment which is made up of physical objects and human users. This environment is responsible for information exchange with the system, but also for various kinds of unwanted interference.In the sense of the IFIP guide to concepts and terms in Data Processing (Gould 71) : "a representation of facts or ideas in a formalized manner capable of being communicated or manipulated by some prooess". 194In the above general characterization of a system, they ke~ords are "interacting" and "purpose". "Interaction" means that a major part of the designer's activity must be concerned with the proper definition and management of the relations between the parts of a system. Decomposition, modularization and interface definition are one side of this activity; synchronization between parallel processes is another aspect."Purpose" means that a system, or a part of it, has a specific function that must be clearly defined and stated. Proper specification is a necessity if the design and development process is to be kept under control.Computer programming is often referred to as an art rather than a scientific activity (Knuth 74a). Such reference applies more generally to information systems design. A number of factors account for this situation : -User needs and requirements are ill-defined; and when defined, they are often mutually conflicting.Information systems have long lives and interact with a changing and complex environment; therefore, they are subject to constant modification.-Large information systems are very complex creations, which cannot in general be complete...