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Research and Advances

Problems in application software maintenance

The problems of application software maintenance in 487 data processing organizations were surveyed. Factor analysis resulted in the identification of six problem factors: user knowledge, programmer effectiveness, product quality, programmer time availability, machine requirements, and system reliability. User knowledge accounted for about 60 percent of the common problem variance, providing new evidence of the importance of the user relationship for system success or failure. Problems of programmer effectiveness and product quality were greater for older and larger systems and where more effort was spent in corrective maintenance. Larger scale data processing environments were significantly associated with greater problems or programmer effectiveness, but with no other problem factor. Product quality was seen as a lesser problem when certain productivity techniques were used in development.
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Research and Advances

An experimental study of the human/computer interface

An exploratory study was conducted to analyze whether interface and user characteristics affect decision effectiveness and subject behavior in an interactive human/computer problem-solving environment. The dependent variables were performance and the use of the systems options. Two of the independent variables examined, experience and cognitive style, were user characteristics; the other three, dialogue, command, and default types, were interface characteristics. Results indicate that both user and interface characteristics influence the use of the system options and the request for information in the problem-solving task.
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Research and Advances

Authentication of signatures using public key encryption

One of Needham and Schroeder's proposed signature authentication protocols is shown to fail when there is a possibility of compromised keys: this invalidates one of the applications of their technique. A more elaborate mechanism is proposed which does not require a network clock, but does require a third party to the transaction. The latter approach is shown to be reliable in a fairly strong sense.
Research and Advances

The evolution of user behavior in a computerized conferencing system

Data from 18-month operational trials of the EIES system indicate that the range of features considered valuable in a computer-based communication system increases with the amount of experience gained by using this medium of communication. Simple message systems alone are not likely to satisfy the communications needs of long term, regular users of computerized communications systems. Among the capabilities which long term, regular users find valuable are group conferences, notebooks for text composition, and self-defined commands.
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Research and Advances

Documentation for a model: a hierarchical approach

A set of documents and their organization according to functional requirements in order to produce information that will facilitate the use of models are described. The authors discuss the role of models in the policy process and of documentation in the assessment of such models.
Research and Advances

A history and evaluation of System R

System R, an experimental database system, was constructed to demonstrate that the usability advantages of the relational data model can be realized in a system with the complete function and high performance required for everyday production use. This paper describes the three principal phases of the System R project and discusses some of the lessons learned from System R about the design of relational systems and database systems in general.
Research and Advances

An experiment in high level language microprogramming and verification

The STRUM system was created to apply software engineering techniques to microprogramming. It provides the tools that allow the microprogrammer to use high level language, structured programming, and formal program verification to create emulations for a horizontally microprogrammed computer. This system is evaluated in two parts: (1) High level microprogramming language design and its use in structured microprogramming; and (2) Verification of a large microprogram. Both parts of this evaluation include experimental results. Part I includes a comparison of an emulation created using traditional techniques to the same emulation created using the STRUM system. Part II describes the formal verification of a 1700 line program that was immediately subjected to extensive testing. This work provides new results on the efficiency of high level microprogramming languages, the effectiveness of peephole optimization for microcode and the practicality of formal microprogram verification.
Research and Advances

Computer information systems and organization structure

A study of Computer Information Systems and Management (CISM) is described and selected results relating to changes in organizational structure in eight organizations are presented. In five of the organizations no changes in formal structure accompanied the introduction of CIS. Where organizational changes did occur, the existing structure of the organization was usually reinforced. These findings suggest that CIS is a flexible tool that is compatible with a variety of organizational design options and not a cause of design per se.
Research and Advances

A user-friendly algorithm

The interface between a person and a computer can be looked at from either side. Programmers tend to view it from the inside; they consider it their job to defend the machine against errors made by its users. From the outside, the user sees his/her problems as paramount. He/she is often at odds with this complex, inflexible, albeit powerful tool. The needs of both people and machines can be reconciled; users will respond more efficiently and intelligently if they receive meaningful feedback. A “user-friendly” algorithm that covers a wide range of interactive environments and is typical of most operating systems and many application programs is presented.
Research and Advances

Shuffle languages, Petri nets, and context-sensitive grammars

Flow expressions have been proposed as an extension of the regular expressions designed to model concurrency. We examine a simplification of these flow expressions which we call shuffle expressions. We introduce two types of machines to aid in recognizing shuffle languages and show that one such machine may be equivalent to a Petri Net. In addition, closure and containment properties of the related language classes are investigated, and we show that one machine type recognizes at least a restricted class of shuffle languages. Finally, grammars for all shuffle languages are generated, and the shuffle languages are shown to be context-sensitive.
Research and Advances

The Cornell program synthesizer: a syntax-directed programming environment

Programs are not text; they are hierarchical compositions of computational structures and should be edited, executed, and debugged in an environment that consistently acknowledges and reinforces this viewpoint. The Cornell Program Synthesizer demands a structural perspective at all stages of program development. Its separate features are unified by a common foundation: a grammar for the programming language. Its full-screen derivation-tree editor and syntax-directed diagnostic interpreter combine to make the Synthesizer a powerful and responsive interactive programming tool.
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Research and Advances

An abstract programming model

An abstract model of a processor is presented informally. The model can be used by itself to abstractly describe algorithms, or with a direct implementation to write and run programs, or as the foundation of a programming language. In the last case, a translator allows higher level descriptions of algorithms for the model.
Research and Advances

Automatic extension of an ATN knowledge base

A computer program is described that acquires much of its knowledge from conversations among operators on Morse code radio networks. The system consists of a learning component and a language understander. The learning component extends a ‘core’ augmented transition network (ATN) knowledge base by generalizing from sentences taken from scripts of actual conversations. The extensions enable the understanding component to process a large number of sentences that are syntactically and semantically similar to the examples.

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