Software Requirements Engineering

This new edition describes current best practices in requirements engineering with a focus primarily on software systems but also on systems that may contain other elements such as hardware or people. The text consists of original papers, written by experts in the field, plus revisions of papers from the first edition. The book begins with an introduction to current issues and the basic terminology of the software requirements engineering process. The text covers the five phases of software requirements engineering that need to be performed to reduce the chance of software failure: elicitation, analysis, specification, verification, and management.

Software Requirements Engineering, Second Edition:

• Looks at the science and discipline that concern establishing documenting software requirements
• Describes the process through which developers' and users' discover, review, articulate, and understand the users' needs and the constraints on software and development activity
• Shows how to analyze the users' needs to arrive at a definition of their software requirements
• Examines software requirements and the need to clearly document and precisely record each requirement
• Looks at verification to ensure that the software requirements specifications are in compliance with the system requirements and conforms to document standards
• Details software requirements management including planning and controlling of all these activities

• The increased recognition of the importance of requirements engineering and the risks of doing it incorrectly or insufficiently (the inability to produce complete, correct, and unambiguous software requirements) is still considered the major cause of software failure today
• An increase in the number of conferences and workshops devoted exclusively to requirements engineering, for example, the International Symposium on Requirements Engineering, held in odd-numbered years, and the International Conference on Requirements Engineering, held in even-numbered years
• An increased number of books and journals devoted to requirements engineering, for example, Requirements Engineering Journal (Springer-Verlag London, Ltd.), Davis, A.M., Software Requirements: Analysis and Specification (Prentice-Hall International, Englewood Cliffs, N.J.)
• The inclusion, in the Capability Maturity Model for Software (published in 1993 by the Software Engineering Institute), of requirements engineering as a "Key Process Area" in defining a mature software development process
• The increased development of commercially available tools that support requirements engineering functions
• The emergence of subspecialties of requirements engineering, for example, requirements elicitation, requirements verification, and requirements traceability
• More extensive use of the concept of operations (ConOps) document, which was first invented and described in the literature more than 15 years ago
• More extensive practice of the validation and verification of requirements. As with the ConOps document, this is not a new idea, but is now much more accepted

This tutorial describes the current state of the practice of requirements engineering, primarily for software systems but also for systems that may contain other elements such as hardware and people. Every attempt has been made to select good, current tutorial papers for this tutorial. A paper published in the 1980s or even the 1970s is not by definition "old" or out of date. Some very fine papers, published 1~15 years ago, are still current and are the best available description of the subject under consideration. Papers selected for inclusion in this tutorial were carefully checked against the following criteria, to determine if they:

• Accurately described the state of the practice for the given topic; if a small portion of a paper was perhaps outdated, this was explained in the chapter introduction
• Covered the state of the practice for the given topic thoroughly and evenly
• Defined the basic terms
• Avoided presenting new, unproved concepts, with no reasonable prediction as to their future
• Did not try to sell one tool or concept over all others
• Are easy to read, for example, contained no gratuitous (unnecessary) mathematics
• Are organized in a hierarchical manner (top-level concepts discussed first, second-level concepts discussed next, and so forth)
• Provided a list of additional references
• Were written by an expert in the area (to assure all of the above)

Our criteria are, of course, idealized. Even these "rules" were violated if there was a good reason. On the basis of these criteria, we have selected papers in the following six chapters:

Chapter 1:   Introductions, Issues, and Terminology

Chapter 2:   System and Software System Engineering

Chapter 3:   Software Requirements Analysis and Specifications

Chapter 4:   Software Requirements Methodologies and Tools

Chapter 5:   Requirements and Quality Management

Chapter 6:   Software System Engineering Process Models

Where there were good existing papers, either from the first edition of this tutorial or elsewhere, we have used them. A large number of the papers from the first edition are still current and topical. We have also sought out new papers and revisions of papers from the first edition from noted authors in the field.

This tutorial is one of a set of tutorials on "software system engineering" published or to be published by the IEEE Computer Society Press:

• R.H. Thayer (ed.), Software Engineering Project Management,
  IEEE Computer Society Press, Los Alamitos, CA, 1997
• M. Dorfman and R.H. Thayer (eds.), Software Engineering,
  IEEE Computer Society Press, Los Alamitos, CA, 1997
• R.H. Thayer and A.D. McGettrick (eds.), Software Engineering—A European Perspective,
  IEEE Computer Society Press, Los Alamitos, CA, 1993

Duplication of papers across tutorials has been kept to a minimum. In a few cases, particularly important papers are duplicated in order that each tutorial can stand alone.

We would like to acknowledge the support provided by the following people.

• Dr. William (Bill) Sanders, Managing Editor,
  Computer Society Press
• Ms. Cheryl Smith, Acquisitions Assistant,
  Computer Society Press
• Ms. Lisa O'Conner, Tutorial Production Editor,
  Computer Society Press

Merlin Dorfman, PhD
Lockheed Martin Missiles and Space Company
Sunnyvale, California, USA

Richard H. Thayer, PhD
California State University, Sacramento
Sacramento, California, USA

Prior to this, he served over 20 years in the U.S. Air Force as a senior officer in a variety of positions associated with engineering, computer programming, research, teaching, and management in computer science and data processing. His numerous positions include six years as a supervisor and technical leader of scientific programming groups, four years directing the U.S. Air Force R&D program in computer science, and six years of managing large data processing organizations.

Thayer is a Senior Member of the IEEE Computer Society and the IEEE Software Engineering Standards Subcommittee. He is Chairperson for the Working Group for a Standard for a Concept of Operations (ConOps) document and past chairperson for the Working Group for a Standard for a Software Project Management Plans. He is a Distinguished Visitor for the IEEE Computer Society.

He is also an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA) where he served on the AIAA Technical Committee on Computer Systems, and he is a member of the Association for Computing Machinery (ACM). He is also a registered professional engineer.

He has a BSEE and an MS degree from the University of Illinois at Urbana (1962) and a PhD from the University of California at Santa Barbara (1979) all in Electrical Engineering.

He has edited and/or co-edited numerous tutorials for the IEEE Computer Society Press: Software Engineering Project Management (1988), System and Software Requirements Engineering (1990), Software Engineering—European Prospective (1992), and Software Engineering (1996). He is the author of over 40 technical papers and reports on software project management, software engineering, and software engineering standards and is an invited speaker at many national and international software engineering conferences and workshops.

Merlin Dorfman, PhD, is a Technical Consultant in the Space Systems Product Center, Lockheed Martin Missiles and Space Company, Sunnyvale, Calif. He specializes in systems engineering for software-intensive systems (requirements analysis, top-level architecture, and performance evaluation), in software process improvement, and in algorithm development for data processing systems. He has performed concept exploration, system implementation, and operations and maintenance of data systems and has worked on proposal teams and company-funded technology projects as well as on development contracts. He was in charge of the development of the Automated Requirements Traceability System (ARTS). He was the first chairman of Space Systems Division's Software Engineering Process Group. He represented the Lockheed Corporation on the Embedded Computer Software Committee of the Aerospace Industries Association, and was Vice-Chairman of the Committee.

Dorfman wrote and taught a four-day course, "Software Requirements and Design Specifications," for Learning Tree International of Los Angeles, Calif. He co-teaches a two-week course in Software Project Management for the Center for Systems Management of Cupertino, Calif. He has been a guest lecturer on software systems engineering at the Defense Systems Management College. He is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA), a member of its System Engineering Technical Committee, past chairman of the Software Systems Technical Committee, and past Chairman of the AIAA San Francisco Section, and is currently Assistant Director of Region 6 (West Coast). He is an affiliate member of the Institute of Electrical and Electronics Engineers (IEEE) Computer Society.

He has a BS and MS from the Massachusetts Institute of Technology and a PhD from Stanford University, all in Aeronautics and Astronautics. He is a registered Professional Engineer in the states of California and Colorado and is a member of the Tau Beta Pi and Sigma Gamma Tau honorary societies.

He is co-editor of three IEEE Tutorial volumes, System and Software Requirements Engineering; Standards, Guidelines, and Examples for System and Software Requirements Engineering; and Software Engineering and co-editor of a volume, Aerospace Software Engineering, in the AIAA "Progress in Aeronautics and Astronautics" Series. Quotes