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At least 1,279 records · Page 71

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NASA NTRS1983

Monitoring software development through dynamic variables

Research conducted by the Software Engineering Laboratory (SEL) on the use of dynamic variables as a tool to monitor software development is described. Project independent measures which may be used in a management tool for monitoring software development are identified. Several FORTRAN projects with similar profiles are examined. The staff was experienced in developing these types of projects. The projects developed serve similar functions. Because these projects are similar some underlying relationships exist that are invariant between projects. These relationships, once well defined, may be used to compare the development of different projects to determine whether they are evolving the same way previous projects in this environment evolved.

Doerflinger, Carl W.↗

NASA NTRS1985

ARROWSMITH-P: A prototype expert system for software engineering management

Although the field of software engineering is relatively new, it can benefit from the use of expert systems. Two prototype expert systems were developed to aid in software engineering management. Given the values for certain metrics, these systems will provide interpretations which explain any abnormal patterns of these values during the development of a software project. The two systems, which solve the same problem, were built using different methods, rule-based deduction and frame-based abduction. A comparison was done to see which method was better suited to the needs of this field. It was found that both systems performed moderately well, but the rule-based deduction system using simple rules provided more complete solutions than did the frame-based abduction system.

Basili, Victor R.↗

NASA NTRS1985

Criteria for software modularization

A central issue in programming practice involves determining the appropriate size and information content of a software module. This study attempted to determine the effectiveness of two widely used criteria for software modularization, strength and size, in reducing fault rate and development cost. Data from 453 FORTRAN modules developed by professional programmers were analyzed. The results indicated that module strength is a good criterion with respect to fault rate, whereas arbitrary module size limitations inhibit programmer productivity. This analysis is a first step toward defining empirically based standards for software modularization.

Card, David N.↗

NASA NTRS1987

Detection of faults and software reliability analysis

Multi-version or N-version programming is proposed as a method of providing fault tolerance in software. The approach requires the separate, independent preparation of multiple versions of a piece of software for some application. These versions are executed in parallel in the application environment; each receives identical inputs and each produces its version of the required outputs. The outputs are collected by a voter and, in principle, they should all be the same. In practice there may be some disagreement. If this occurs, the results of the majority are taken to be the correct output, and that is the output used by the system. A total of 27 programs were produced. Each of these programs was then subjected to one million randomly-generated test cases. The experiment yielded a number of programs containing faults that are useful for general studies of software reliability as well as studies of N-version programming. Fault tolerance through data diversity and analytic models of comparison testing are discussed.

Knight, John C.↗

NASA NTRS1985

Software error experiment

The goal was to develop analytic methods to prove performance properties and to measure reliability properties of software. Charts on software reliability studies and on a software error experiment are given.

Holt, H. Milton↗

NASA NTRS1985

Software life cycle dynamic simulation model: The organizational performance submodel

The submodel structure of a software life cycle dynamic simulation model is described. The software process is divided into seven phases, each with product, staff, and funding flows. The model is subdivided into an organizational response submodel, a management submodel, a management influence interface, and a model analyst interface. The concentration here is on the organizational response model, which simulates the performance characteristics of a software development subject to external and internal influences. These influences emanate from two sources: the model analyst interface, which configures the model to simulate the response of an implementing organization subject to its own internal influences, and the management submodel that exerts external dynamic control over the production process. A complete characterization is given of the organizational response submodel in the form of parameterized differential equations governing product, staffing, and funding levels. The parameter values and functions are allocated to the two interfaces.

Tausworthe, Robert C.↗

NASA NTRS1985

The SIFT hardware/software systems. Volume 2: Software listings

This document contains software listings of the SIFT operating system and application software. The software is coded for the most part in a variant of the Pascal language, Pascal*. Pascal* is a cross-compiler running on the VAX and Eclipse computers. The output of Pascal* is BDX-390 assembler code. When necessary, modules are written directly in BDX-390 assembler code. The listings in this document supplement the description of the SIFT system found in Volume 1 of this report, A Detailed Description.

Palumbo, Daniel L.↗

NASA NTRS1987

A controlled experiment on the impact of software structure on maintainability

The impact of software structure on maintainability aspects including comprehensibility, locality, modifiability, and reusability in a distributed system environment is studied in a controlled maintenance experiment involving six medium-size distributed software systems implemented in LADY (language for distributed systems) and six in an extended version of sequential PASCAL. For all maintenance aspects except reusability, the results were quantitatively given in terms of complexity metrics which could be automated. The results showed LADY to be better suited to the development of maintainable software than the extension of sequential PASCAL. The strong typing combined with high parametrization of units is suggested to improve the reusability of units in LADY.

Rombach, Dieter H.↗

NASA NTRS1987

Software reliability models for fault-tolerant avionics computers and related topics

Software reliability research is briefly described. General research topics are reliability growth models, quality of software reliability prediction, the complete monotonicity property of reliability growth, conceptual modelling of software failure behavior, assurance of ultrahigh reliability, and analysis techniques for fault-tolerant systems.

Miller, Douglas R.↗

NASA NTRS1987

Software reliability perspectives

Software which is used in life critical functions must be known to be highly reliable before installation. This requires a strong testing program to estimate the reliability, since neither formal methods, software engineering nor fault tolerant methods can guarantee perfection. Prior to the final testing software goes through a debugging period and many models have been developed to try to estimate reliability from the debugging data. However, the existing models are poorly validated and often give poor performance. This paper emphasizes the fact that part of their failures can be attributed to the random nature of the debugging data given to these models as input, and it poses the problem of correcting this defect as an area of future research.

Wilson, Larry↗

NASA NTRS1987

Experiments in fault tolerant software reliability

The reliability of voting was evaluated in a fault-tolerant software system for small output spaces. The effectiveness of the back-to-back testing process was investigated. Version 3.0 of the RSDIMU-ATS, a semi-automated test bed for certification testing of RSDIMU software, was prepared and distributed. Software reliability estimation methods based on non-random sampling are being studied. The investigation of existing fault-tolerance models was continued and formulation of new models was initiated.

Mcallister, David F.↗

NASA NTRS1987

Software for integrated manufacturing systems, part 1

For several years, a broad, unified approach to programming manufacturing cells, factory floors, and other manufacturing systems has been developed. It is based on a blending of distributed Ada, software components, generics and formal models. Among other things the machines and devices which make up the components, and the entire manufacturing cell is viewed as an assembly of software components. The purpose of this project is to reduce cost, increase the reliability and increase the flexibility of manufacturing software. An overview is given of the approach and an experimental generic factory floor controller that was developed using the approach is described. The controller is generic in the sense that it can control any one of a large class of factory floors making an arbitrary mix of parts.

Naylor, A. W.↗

NASA NTRS1988

The Environment for Application Software Integration and Execution (EASIE) version 1.0. Volume 4: System installation and maintenance guide

The Environment for Application Software Integration and Execution (EASIE) provides both a methodology and a set of software utility programs to ease the task of coordinating engineering design and analysis codes. This document provides necessary information for installing the EASIE software on a host computer system. The target host is a DEX VAX running VMS version 4; host dependencies are noted when appropriate. Relevant directories and individual files are identified, and compile/load/execute sequences are specified. In the case of the data management utilities, database management system (DBMS) specific features are described in an effort to assist the maintenance programmer in converting to a new DBMS. The document also describes a sample EASIE program directory structure to guide the program implementer in establishing his/her application dependent environment.

Randall, Donald P.↗

NASA NTRS1988

Models and metrics for software management and engineering

This paper attempts to characterize and present a state of the art view of several quantitative models and metrics of the software life cycle. These models and metrics can be used to aid in managing and engineering software projects. They deal with various aspects of the software process and product, including resources allocation and estimation, changes and errors, size, complexity and reliability. Some indication is given of the extent to which the various models have been used and the success they have achieved.

Basili, V. R.↗

NASA NTRS1988

Automated software development workstation

A workstation is being developed that provides a computational environment for all NASA engineers across application boundaries, which automates reuse of existing NASA software and designs, and efficiently and effectively allows new programs and/or designs to be developed, catalogued, and reused. The generic workstation is made domain specific by specialization of the user interface, capturing engineering design expertise for the domain, and by constructing/using a library of pertinent information. The incorporation of software reusability principles and expert system technology into this workstation provide the obvious benefits of increased productivity, improved software use and design reliability, and enhanced engineering quality by bringing engineering to higher levels of abstraction based on a well tested and classified library.

Prouty, Dale A.↗

NASA NTRS1988

Advanced information processing system: Input/output network management software

The purpose of this document is to provide the software requirements and specifications for the Input/Output Network Management Services for the Advanced Information Processing System. This introduction and overview section is provided to briefly outline the overall architecture and software requirements of the AIPS system before discussing the details of the design requirements and specifications of the AIPS I/O Network Management software. A brief overview of the AIPS architecture followed by a more detailed description of the network architecture.

Nagle, Gail↗

NASA NTRS1987

Comparing the effectiveness of software testing strategies

This study compares the results of code reading, functional testing, and structural testing in three aspects of software testing: fault detection effectiveness, fault detection cost, and classes of faults detected. Thirty two professional programmers and 42 advanced students applied the three techniques to four unit-sized programs in a fractional experimental design. The major results of this study are the following: (1) With the professional programmers, code reading detected more software faults and had a higher detection rate than did functional or structural testing, while functional testing detected more faults than did structural testing, but functional and structural testing were not different in fault detection rate. (2) In one advanced student subject group, code reading and functional testing were not different in faults found, but were superior to structural testing, while in the other advanced student subject group there was no difference among the techniques. (3) With the advanced student subjects, the three techniques were not different in fault deteciton rate. (4) Number of faults observed, fault detection rate, and total effort in detection depended on the type of software tested. (5) Code reading detected more interface faults than did the other methods. (6) Functional testing detected more control faults than did the other methods. (7) When asked to estimate the percentage of faults detected, code readers gave the most accurate estimates while functional testers gave the least accurate estimates. Appendix B includes the source code for the word.

Basili, Victor R.↗

NASA NTRS1988

Numerical arc segmentation algorithm for a radio conference - A software tool for communication satellite systems planning

A detailed description of a Numerical Arc Segmentation Algorithm for a Radio Conference (NASARC) software package for communication satellite systems planning is presented. This software provides a method of generating predetermined arc segments for use in the development of an allotment planning procedure to be carried out at the 1988 World Administrative Radio Conference (WARC - 88) on the use of the GEO and the planning of space services utilizing GEO. The features of the NASARC software package are described, and detailed information is given about the function of each of the four NASARC program modules. The results of a sample world scenario are presented and discussed.

Whyte, W. A.↗