Browse Prior Art Database

Software Reliability is Not an Equation

IP.com Disclosure Number: IPCOM000131323D
Original Publication Date: 1978-Jun-01
Included in the Prior Art Database: 2005-Nov-10
Document File: 3 page(s) / 19K

Publishing Venue

Software Patent Institute

Related People

Glenford J. Myers: AUTHOR [+3]

Abstract

M oranda's remarks in The Open Channel in Computer, April 1978, on my book, Software Reliability: Principles and Practices, fall into two general areas. First, he feels that the book ";is not about software reliability as it has come to be defined."; Second. he seems defensive about my ";low opinion"; (his words) of probability-based models. particularly his model.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 31% of the total text.

Page 1 of 3

THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1978 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

Software Reliability is Not an Equation

The Open Channel is exactly what the name implies: a forum for the free exchange of technical ideas. Try to hold your contributions to one page maximum in the final magazine format (about 1000 words).

We'll accept anything (short of libel or obscenity) so long as it's submitted by a member of the Computer Society. If it's really bizarre we may require you to get another member to cosponsor your item.

Send everything to Jim Haynes, Applied Sciences, UC Santa Crud, CA 95064.

Glenford J. Myers

M oranda's remarks in The Open Channel in Computer, April 1978, on my book, Software Reliability: Principles and Practices, fall into two general areas. First, he feels that the book "is not about software reliability as it has come to be defined." Second. he seems defensive about my "low opinion" (his words) of probability-based models. particularly his model.

Concerning the first point, he never bothered to give us his opinion of what software reliability means, but the inference of his remarks is that software reliability is just a matter of numbers -- for instance, predictions of MTTF, the number of errors in a program, and the like. I agree that this is related to software reliability, but it is only a small part. If we use the Program Committee of the 1975 International Conference on Reliable Software as mediators, one sees, by scanning the conference proceedings, that such topics as design, testing, languages, program proving, and management issues are considered important components in the study of software reliability.

I don't have a "low opinion" of reliability models; rather, I am skeptical and am waiting to be convinced, and this is the message I conveyed in my book. If one studies the Jelinski/ Moranda model, one sees that it is the old constant-hazard-rate hardware

reliability model. The only change they made was to introduce a series of models: whenever an error is repaired. a new model is applied having a lower. but still constant. hazard function.

I am skeptical of this model because. as we know. software reliability differs sharply from hardware reliability. The modeling of software reliability entails the modeling of two types of human behavior. First, software doesn't wear out: it fails because of a mistake made by a human designer. Second. software reliability is not time-dependent: whether or not a compiler will fail in the next hour is dependent upon the inputs fed to the compiler by its users. Since Moranda's model is based on the hardware model of purely timedepe...