Table Of ContentSoftware Science and Engineering
Series Editor: Richard A. DeMilio
Purdue University, West Lafayette, Indiana
High-Integrity Software
Edited by C. T. Sennett
Software Reuse: Guidelines and Methods
James W. Hooper and Rowena O. Chester
A Continuation Order Plan is available for this series. A continuation order will bring delivery of
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Software Reuse
Guidelines and Methods
Software Reuse
Guidelines and Methods
w.
James Hooper
The University of Alabama in Huntsville
Huntsville, Alabama
aud
Rowena O. Chester
Martin Marietta Energy Systems
Oak Ridge, Tennessee
Springer Science+Business Media, LLC
Llbrary of Congress Cataloglng-ln-Publlcatlon Data
Hooper, Ja~es W.
Software reu se : guldellnes and ~ethods / James W. Hooper and
Rowena O. Chester.
p. cm. -- (Software sclence and englneerlng)
Includes blbl10graphlcal references and Index.
ISBN 978-1-4613-6677-5 ISBN 978-1-4615-3764-9 (eBook)
DOI 10.1007/978-1-4615-3764-9
1. Co~p~ter software--Reusabl11ty. I. Chester, R. O. II. Tltle.
III. Serles.
CA76.76.R47H66 1991
006--dc20 91-12080
CIP
© 1991 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1991
Ali rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted
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Foreword
Observers in the present usually have an advantage when it comes
to interpreting events of the past. In the case of software reuse, how
ever, it is unclear why an idea that has gained such universal accep
tance was the source of swirling controversy when it began to be taken
seriously by the software engineering community in the mid-1980's.
From a purely conceptual point of view, the reuse of software de
signs and components promises nearly risk-free benefits to the devel
oper. Virtually every model of software cost and development effort
predicts first-order dependencies on either products size or the num
ber of steps carried out in development. Reduce the amount of new
product to be developed and the cost of producing the product de
creases. Remove development steps, and total effort is reduced. By
reusing previously developed engineering products the amount of new
product and the number of development steps can be reduced. In this
way, reuse clearly has a major influence on reducing total development
cost and effort. This, of course, raises the issue of from whence the
reused products arise. There has to be a prior investment in creating
"libraries of reuse products before reuse can be successfuL .. " How
can organizations with a "bottom line" orientation be enticed into
contributing to a reuse venture? Fortunately, the economics of reuse
resembles many other financial investment situationsl. The relevant
index is the ratio Q = i, where, for a total reuse investment R, B
is the resulting cost-benefit, i.e., the difference between the cost of
the activity without reuse and the cost of the activity with the reuse
investment. As Q decreases, the reuse investment becomes more ad
vantageous. If, on the other hand, Q is greater than 1, the benefits of
reuse do not justify the investment.
Furthermore, reuse also has quality implications. Reused compo
nents have, by definition, an operational history that can be used to
predict their future behavior. This is itself a kind of reuse byexploit
ing the experience with reuse library elements, new developers can
make more informed risk assessments for a new project.
1 Barnes, B. and T. Bollinger. 1991. "Making Reuse Cost
Effective." IEEE Software, 8(1), 13-24.
v
VI SOFTWARE REUSE GUIDELINES AND METHODS
None of these ideas were born in a vacuum. By the early 1970's
there had already been highly successful software enterprises based
on reuse. Important lessons were learned and some models were sug
gested for new enterprises. The most celebrated example along these
lines was the growth of mathematical libraries.
These are, in fact, the very aspects of reuse that have contributed
to its success as a software engineering principle. Developers, argu
ing from first principles, apparently could construct a compelling case
that software reuse should be a cornerstone of standard practice. Con
troversies arose, not over the concept, but rather over its applicability
in realistic environments.
Take, for example, the potential cost savings in a reuse environ
ment. The argument that reuse reduces overall costs is based on the
assumption that retrieving and reusing components or designs from a
library is less expensive than recreating them. If all the costs of reuse
were associated with archival characteristics, there would certainly
be no disagreement over the benefits of reuse. But there are other
costs that creep into the picture - interface costs, for example. If N
reuse modules with average size M have to interoperate with pairwise
distinct interfaces, on the order of (~) interface might be required.
The total cost of constructing these interfaces could easily outstrip
the cost of constructing a program of size N . M without reuse.
The quality of reusable components is, of course, a significant risk
factor. How does a developer know when a reused component has
acceptable reliability, suddenly makes unsafe an otherwise safe system,
or degrades system performance? Where is the quality history of a
component stored? Do tests of components in reuse libraries have to
be reexecuted?
The very question of what constitutes a library of reusable soft
ware component is not easy to answer. Examples of successful reuse
such as math libraries are not as easy to generalize as it might seem.
Mathematical software happens to be a field in which the appropriate
"chunk size" is given by the application: a function that implements a
standard numerical algorithm is exactly the right size. But there are
areas in which there are not convenient chunks. What is the appropri
ate component in such an environment? Perhaps more importantly:
can a library be constructed that facilitates user access to needed
components?
Even the investment aspects of reuse present problems to software
engineering projects. Software development are characterized their
susceptibility to schedule and budget pressures, and the sociological
processes that would lead a manager with short-term objectives to
FOREWORD Vll
make a long-term investment in reuse were not defined to any useful
degree.
The US Army Institute for Research in Management Information,
Communications, and Computer Sciences (AIRMICS) had recognized
that effective programs for reuse and the supporting technology would
be difficult to develop without principles, "lessons-learned", and case
studies to guide managers and engineers. AIRMICS initiated and sup
ported the study that led to the present volume. When the history of
software engineering in the 1980's is written, this study will be recog
nized as a pivotal event in the birth of one of the key generalizations
of software engineering - one of the concepts that helped turn it from
a cottage industry to an engineering technology.
Richard A. DeMillo
Washington, DC
February 1991
Preface
Software reuse is currently receiving a great deal of attention. This
interest is fueled by the urgent need for greater software productivity
and quality, coupled with the growing belief that software reuse may
be able to help with these problems. Conferences and workshops on
software engineering or the Ada language are almost certain to have
some papers on reuse-and perhaps multiple sessions devoted to the
topic. Refereed software engineering journals are publishing many
articles on reuse as well.
This book attempts to achieve two related goals:
(a) providing a cogent summary of current research and practice
in software reuse, and
(b) providing practical suggestions for integrating software reuse
into a software engineering process.
The first goal is important because the body of literature is now very
large, and the field is so broad that it is difficult to gain a good grasp of
the issues. We have developed a framework for presenting the material
that should help the reader achieve a perspective of the field. We have
condensed a great deal of material covering both research and practice.
Some of it is useful now, while some of it provides insights into issues
whose solution will permit future gains from reuse. Even though
some incompletely resolved issues remain, we believe that benefits
can be gained now from software reuse-thus leading to the second
goal stated above. This book includes guidelines for integrating reuse
into a software engineering process and for conducting reuse activities.
We sought to propose guidelines that are not dogmatic, but rather
suggestive of important activities and approaches. The guidelines may
alternatively be viewed as summarizing current knowledge about reuse
practice. The level of detail of the guidelines varies depending on how
well the issues are currently understood. We hope they will be helpful
as presented and that in time each organization that undertakes reuse
will evolve its own set of tailored guidelines.
Various audiences should find this book useful. Software engineer
ing managers and practitioners should benefit from the guidelines,
with their supporting rationale, and from descriptions of successful
IX
x SOFTWARE REUSE GUIDELINES AND METHODS
reuse projects. The presentation of research and practice material in
an intelligible framework, augmented by the extensive bibliography,
should be useful to computer science and software engineering educa
tors and students as well as researchers in universities, government,
and industry. Multiple approaches and viewpoints are discussed for
many reuse issues to provide a basis for further experimentation and
research. Discussions of specific research and practice findings are ac
companied by references to the literature; thus the book contains in
essence an extensive annotated bibliography, which can be a valuable
resource to researchers.
We developed and issued much of this material under the Ada
Reuse and Metrics Project (Hooper and Chester 1990), conducted by
Martin Marietta Energy Systems under contract to the U.S. Army
Institute for Research in Management Information, Communications,
and Computer Sciences (AIRMICS). We express our appreciation to
Dan Hocking, who served as the project manager for that work at
AIRMICS. His insightful comments and suggestions led to the devel
opment of more useful results than would otherwise have been the
case, and this book has in turn benefitted. Funding for the AIRMICS
Ada Reuse and Metrics Project was provided by the U.S. Depart
ment of Defense (DOD) Software Technology for Adaptable, Reliable
Systems (STARS) program. Other technical contributors to the Ada
Reuse and Metrics Project included Victor R. Basili (University of
Maryland, College Park); Terry B. Bollinger (CONTEL); Richard A.
DeMillo (Purdue University); Richard E. Fairley (George Mason Uni
versity); Ross A. Gagliano (Georgia State University); Arthur Jones
(Morehouse College); Roger King (University of Colorado at Boul
der); Rhonda Martm (Purdue University); W. Michael McCracken
(Georgia Institute of Technology); Charles W. McKay (University of
Houston, Clear Lake); Shari Lawrence Pfieeger (CONTEL); and H.
Dieter Rombach (University of Maryland, College Park).
We express our appreciation to James Baldo and Ruben Prieto
Diaz for reviewing and commenting on the manuscript. A number of
improvements resulted from their suggestions. We also thank Patricia
Mucke for her invaluable editorial assistance and Ramez Abi Akar for
his careful reading of the manuscript.
James W. Hooper
Huntsville, Alabama
Rowena O. Chester
Oak Ridge, Tennessee
February 1991
Contents
Acronyms . xv
1. Background and Introduction
1.1 The Problem 1
1.2 Concepts and Definitions 2
1.3 Research Activities 4
1.4 Status of Reuse Practice 6
1.5 Scope and Organization of this Book 10
1.6 References . 11
2. Managerial Guidelines
2.1 Managerial Issues and Approaches . 17
2.1.1 Organizational Management and Structure 18
2.1.2 Organizational Behavior 22
2.1.3 Contractual and Legal Considerations 23
2.1.4 Financial Considerations 26
2.1.5 Case Study: Reuse Program at Hartford Insurance
Group 32
Xl
