"No Silver Bullet—Essence and Accident in Software Engineering" is a paper on software engineering written by Fred Brooks in 1986. Brooks argues that "there is no single development, in either technology or management technique, which by itself promises even one order of magnitude [tenfold] improvement within a decade in productivity, in reliability, in simplicity." He also states that "we cannot expect ever to see two-fold gains every two years" in software development, as there is in hardware development (Moore's law).

Summary

Brooks distinguishes between two different types of complexity: accidental complexity and essential complexity. This is related to Aristotle's classification. Accidental complexity relates to problems that engineers create and can fix. For example, modern programming languages have abstracted away the details of writing and optimizing assembly language source code and eliminated the delays caused by batch processing, though other sources of accidental complexity remain. Essential complexity is caused by the problem to be solved, and nothing can remove it; if users want a program to do 30 different things, then those 30 things are essential and the program must do those 30 different things.

Brooks claims that accidental complexity has decreased substantially, and today's programmers spend most of their time addressing essential complexity. Brooks argues that this means shrinking all the accidental activities to zero will not give the same order-of-magnitude improvement as attempting to decrease essential complexity. While Brooks insists that there is no one silver bullet, he believes that a series of innovations attacking essential complexity could lead to significant improvements. One technology that had made significant improvement in the area of accidental complexity was the invention of high-level programming languages, such as Ada.

Brooks's paper has sometimes been cited in connection with Wirth's law, to argue that "software systems grow faster in size and complexity than methods to handle complexity are invented."

See also

  • History of software engineering
  • Software prototyping, one of the main strategies against essential complexity in "No Silver Bullet"
  • SOLID
  • Essential complexity

References

Further reading

  • No Silver Bullet — Essence and Accident in Software Engineering, by Frederick P. Brooks, Jr.
  • Software Engineering Principles—Steve McConnell's comments on the dichotomy, originally published in IEEE Software, Vol. 16, No. 2, March/April 1999