Details of a scientific approach to information systems, Courant Symp. in Data Base Systems

are the optimal strategy for the usage considered. If it is assumed now that all q s = 0 (i.e. there is no querying to the IPS) then it is clear that no indexing path is profitable. Rule 4 If only queries and no maintenance are performed then all the candidate indexing paths are included in the optimal strategy whereas if maintenance only is done, no indexing path appears in the IPS. Conclusions A file designer who cannot determine the effects of each alternative decision is bound to make subjective or intuitive design judgements instead of objective ones. The properties and rules stated (a) provide the means to improve the performance of IPS by expanding the current spectrum of alternative indexing paths examined prior to making any implementation decision, and (b) provide for increased confidence in the decision made. In Book review A Programming Metholodology in Compiler Construction Part I: Concepts by J. Lewi, K. De Vlaminck, J. Huens and M. Huybrechts, 1979; 308 pages. (North-Holland, $41.50) In the late 1950s the task of compiler construction was considered a major undertaking. The first FORTRAN compiler, for example, took 18 man-years to implement (Backus et al, 1957). Now, in the late 1970s, such a task is considered a reasonable computer science student project. The factors that have led to this over the last twenty years are (a) the comprehension of the organisation and modular design of the compilation process, (b) the development of systematic techniques for handling the majority of the important tasks that occur during compilation and (c) the construction of software tools that assist in the implementation of compilers and compiler components. Implicit in all these three developments is the closing of the gap between theory and practice. This book is the first part of a twopart description of an environment utilising a completely closed gap. Part I introduces the basic theoretical models whilst part 2 will consider the more practical aspects of the engineering of the environment (namely the language implementation laboratory [LILA] [transducer] programs from the associated syntax. As such, each section is the logical progression of the previous and the methodology used in each section is a reflection of the methodology of the previous section. Hence the book is structurally pleasing and easy to read. In conclusion, the book is ideally suited to the software engineer who is actively involved in the application of language theory to compiler construction (or the construction of any systems softwar