International Software Process Association (ISPA)

author(s): Kathleen Culver-Lozo, Susan Linnell
title: The Impact of Software Process Improvement on Interval, Cost and Quality: Strategies for Success
organisation(s): Bell Laboratories Lucent Technologies, Inc. (formerly AT&T)

The Impact of Software Process Improvement on Interval, Cost and Quality: Strategies for Success


Software process improvement (SPI) initiatives are a generally accepted strategy for improving the performance of a software development organization. Managers contract assessments from a variety of sources to identify gaps in the existing process and to create improvement plans to close gaps and improve assessment scores. The underlying assumption made by many of these development organizations is that an improvement in the scores result in some proportional improvement in development costs, development interval, or software quality. While case studies have presented a relationship between scores and performance and correlations have been established, causality between an increase in scores and an increase in performance has not been proven. This paper examines some of the reasons why maximizing an assessment score may not maximize the bottom line given our experiences with software process engineering at Lucent Technologies for the past eight years. These experiences may tempt some managers to conclude that SPI initiatives, like CASE tools in the `80's, are simply the latest fad to address the challenges of software development. We counter this conclusion with the position that a mature software development organization, as measured by software assessments, is an essential ingredient, but not the only ingredient, for sustained software development performance.


An assessment typically rates the organization on the answers provided by project members to a set of questions. The answers are compiled and a `level' is assigned to or profile developed for the organization. Because the focus of the assessments is on the software development infrastructure, efforts to improve assessment scores will emphasize improvements to the development infrastructure. But a strong structure to support software development, although critical to sustained improvements in performance, is not sufficient to achieve breakthroughs in interval, cost, and quality. The organization must also carefully manage what goes into the infrastructure and the context in which it operates.

Given the experiences with software process engineering at Bell Labs, the following factors are also critical to the bottom line impact of an SPI effort:


Some projects at Lucent Technologies have improved their assessment scores without substantially improving their performance on interval, cost, and quality measures. The previous section has suggested some reasons why this may have happened. However, many projects have experienced improvements in performance which have been correlated to efforts to improve assessment scores. For these projects, improving the process infrastructure is what was necessary to improve performance.

Other projects have improved performance without embarking upon deliberate SPI efforts. We believe that these projects will find it difficult to make continued improvements if their infrastructure lacks:


Given these experiences the following actions are recommended to maximize the impact of an SPI initiative on the bottom line:

Table of Contents
Sessions 1 & 2

ISPA Homepage - This information last updated October 1997
Copyright © 1996-7. All rights reserved.