David Parnas

David Lorge Parnas (born February 10, 1941) is a Canadian early pioneer of software engineering, who developed the concept of information hiding in modular programming, which is an important element of object-oriented programming today. He is also noted for his advocacy of precise documentation.

David Parnas
Born (1941-02-10) February 10, 1941
Plattsburgh, New York, United States
Known forInformation hiding, Strategic Defense Initiative activism
Scientific career
Doctoral advisorAlan Perlis
Everard Mott Williams
Doctoral studentsRichard J. Lipton
Steven M. Bellovin


Parnas earned his Ph.D. at Carnegie Mellon University in electrical engineering. Parnas also earned a professional engineering license in Canada and was one of the first to apply traditional engineering principles to software design. He worked there as a professor for many years. He also taught at the University of North Carolina at Chapel Hill (U.S.), at the Department of Computer Science of the Technische Universität Darmstadt (Germany), the University of Victoria (British Columbia, Canada), Queen's University in Kingston, Ontario, McMaster University in Hamilton, Ontario, and University of Limerick (Republic of Ireland).

David Parnas received a number of awards and honors:


Modular design

In modular design, his double dictum of high cohesion within modules and loose coupling between modules is fundamental to modular design in software. However, in Parnas's seminal 1972 paper On the Criteria to Be Used in Decomposing Systems into Modules, this dictum is expressed in terms of information hiding, and the terms cohesion and coupling are not used. He never used them. [3]

Technical activism

Dr Parnas took a public stand against the US Strategic Defense Initiative (also known as "Star Wars") in the mid 1980s, arguing that it would be impossible to write an application of sufficient quality that it could be trusted to prevent a nuclear attack.[4] He has also been in the forefront of those urging the professionalization of "software engineering" (a term that he characterizes as "an unconsummated marriage"). Dr. Parnas is also a heavy promoter of ethics in the field of software engineering.

Stance on academic evaluation methods

Parnas has joined the group of scientists which openly criticize the number-of-publications-based approach towards ranking academic production. On his November 2007 paper Stop the Numbers Game,[5] he elaborates on several reasons on why the current number-based academic evaluation system used in many fields by universities all over the world (be it either oriented to the amount of publications or the amount of quotations each of those get) is flawed and, instead of generating more advance of the sciences, it leads to knowledge stagnation.


  • Parnas, D.L. (December 1972). "On the Criteria To Be Used in Decomposing Systems into Modules". Communications of the ACM. 15 (12): 1053–58. doi:10.1145/361598.361623.

See also


  1. RSC Fellow search, retrieved 2018-01-04.
  2. GI-Fellow citation Archived 2011-08-13 at the Wayback Machine, retrieved 2012-03-09.
  3. Parnas 1972.
  4. Parnas D.L. (December 1985). "Software aspects of strategic defense systems". Comm ACM. 28 (12): 1326–35. doi:10.1145/214956.214961.
  5. Parnas, David (November 2007). "Stop the Numbers Game". Communications of the ACM. 50 (11): 19–21. doi:10.1145/1297797.1297815.

Further reading

  • Hoffman, Daniel M.; Weiss David M. (eds.): Software Fundamentals – Collected Papers by David L. Parnas, 2001, Addison-Wesley, ISBN 0-201-70369-6.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.