VLSI and software engineering: Guest editor's introduction

This paper describes an IEEE Computer Society Workshop on the subject of VLSI and Software Engineering and introduces five papers that were generated as a result of the workshop. Also presented here are some thoughts on parallels between the two disciplines.     

Module size: A standard or heuristic?

Current and proposed national software development specifications include module size limits in the form of an upper bound per module and an average for a group of modules. This paper claims that commonly specified limits such as 200 executable source statements have little practical value for programmers, and that the limits have not been validated. Module size guidelines based on corresponding complexity are derived for identifying extremly long modules, and are recommended for use by software quality engineers in monitoring development methodologies and by test engineers during preacceptance testing. Finally, research to derive a lower bound guideline for module size is recommended.     

An experiment with affirm and HDM

Comparing the usefulness of methodologies for software development can be especially difficult when the services offered are based on different philosophies. Two systems, Affirm and HDM, were compared for their application to operation system security analysis. The assessment technique was to specify and analyze for security flaws on both systems a miniature example of a security kernel. The specification languages are at the opposite poles of the range from algebraic axioms to transition specifications. The types of security properties that could be verified with the tools available were access policy invariants and information flows. One theorem prover was highly interactive and the other nearly automatic. We found that the example could be specified satisfactorily and recognizably on both systems with a comparable amount of effort. The security analyses, on the other hand, led to very different verification tasks and different results. The two results were complementary rather than contradictory, and some additional experimentation, guided by theoretical suspicions, showed the exact relationship between them.     

Status and outlook for DoD configuration management requirements

Since the release of Department of Defense (DoD) Directive 5000.29, “Management of Computer Resources in Major Defense Systems,” 26 April 1976, a significant increase in interest and emphasis on software configuration management has occurred. A review of the current status of configuration management within the DoD computer resources management environment is provided, and some predictions on future configuration management activities are offered.     

Implementation of computing standards

The F-16 avionics implements what is likely the broadest application of standards of any USAF weapon system. Standards available in 1976 were applied which consisted of the MIL-STD-1553 Multiplex Data Bus, JOVIAL J3B which was the defacto software and precursor to JOVIAL J73 dialect and the MIL-STD-490 software documentation standard. These standards were instrumental in making the F-16 a very successful program. The F-16 avionic system is now being greatly expanded to accommodate advanced sensors and weapons currently in USAF funded development. Once again the F-16 is at the forefront in implementing the latest USAF standards. A key feature of the enhanced avionics is the application of JOVIAL J73 (MIL-STD-1589B) for all subsystems, the MIL-STD-1553B Multiplex Data Bus, the MIL-STD-1750A Computer Instruction Set Architecture, and the MIL-STD-1760 Stores Interface. Both the implementation of standards in the current F-16 avionics and also in the enhanced F-16 avionics now in development are described.     

High-level testing and example-directed development of software specifications

A testing-based approach for constructing and refining very high-level software functionality representations such as intentions, natural language assertions, and formal specifications is presented and applied to a standard line-editing problem as an illustration. The approach involves the use of specification-based (black-box) test-case generation strategies, high-level specification formalisms, redundant or parallel development and cross-validation, and a logic programming support environment. Test-case reference sets are used as software functionality representations for the purposes of cross-validating two distinct high-level representations, and identifying ambiguities and omissions in those representations. In fact, we propose the use of successive refinements of such test reference sets as the authoritative specification throughout the software development process. Potential benefits of the approach include improvements in user/ designer communication over all life cycle phases, and an increase in the quality of specifications and designs.     

The functional life cycle model and its automation: USE.IT

Recently there has been an accelerated awareness of the urgent need for effective system development tools and techniques. Towards this end attempts have been made to develop standard languages for programming and standard techniques for the front end of the development process. Further, there has even been talk of integrating the various processes within a system life cycle. Our thesis, here, is that although these are steps leading in the right direction, they are simply not enough. What we suggest is needed, rather, is a totally new life cycle model; it is based on pure functional needs. This is in contrast to the “event” driven model that has been forced into being based on constraints which are often unnecessary, wasteful, and error prone. The functional model, itself formally defined, not only includes formal techniques for defining the front end, but it also includes techniques which integrate by means of formal methods and automation that front end to the rest of the life cycle of a system. A functional life cycle model has been defined. USE.IT, an implementation of this model, provides for an integrated and automated development process of a system. We discuss, here, the HOS functional model, USE.IT, and the implications of their use.     

Correct: A simulated text editor

This paper describes a project to write a simulator for the native mode text editor of one computer, which could be run on a different computer. This was done to give a user of both computers a common editing language. The method of design and construction is presented together with brief details of the syntax and semantics of the editing language.     

Programming methodology,organizational environment,and programming productivity

Programming data involving 278 commercial-type programs were collected from 23 medium- to large-scale organizations in order to explore the relationships among variables measuring program type, the testing interface, programming technique, programmer experience, and productivity. Programming technique and programmer experience after 1 year were found to have no impact on productivity, whereas on-line testing was found to reduce productivity. A number of analyses of the data are presented, and their relationship to other studies is discussed.     

Software complexity and software maintenance: A survey of empirical research

A number of empirical studies have pointed to a link between software complexity and software maintenance performance. The primary purpose of this paper is to document what is known about this relationship, and to suggest some possible future avenues of research. In particular, a survey of the empirical literature in this area shows two broad areas of study: complexity metrics and comprehension. Much of the complexity metrics research has focused on modularity and structure metrics. The articles surveyed are summarized as to major differences and similarities in a set of detailed tables. The text is used to highlight major findings and differences, and a concluding remarks section provides a series of recommendations for future research.     

Speech understanding systems: Report of a steering committee

A five-year interdisciplinary effort by speech scientists and computer scientists has demonstrated the feasibility of programming a computer system to “understand” connected speech, i.e., translate it into operational form and respond accordingly. An operational system (HARPY) accepts speech from five speakers, interprets a 1000-word vocabulary, and attains 91 percent sentence accuracy. This Steering Committee summary report describes the project history, problem, goals, and results.