Brooks's law is an observation about
software project management
Software project management is the process of planning and leading software projects. It is a sub-discipline of project management in which software projects are planned, implemented, monitored and controlled.
History
In the 1970s and 1980s, ...
that "Adding manpower to a late software project makes it later."
[Frederick P. Brooks, Jr. '']The Mythical Man-Month
''The Mythical Man-Month: Essays on Software Engineering'' is a book on software engineering and project management by Fred Brooks first published in 1975, with subsequent editions in 1982 and 1995. Its central theme is that adding manpower to a s ...
''. 1995 975 Addison-Wesley. It was coined by
Fred Brooks
Frederick Phillips Brooks Jr. (April 19, 1931 – November 17, 2022) was an American computer architect, software engineer, and computer scientist, best known for managing development of IBM's System/360 family of mainframe computers and the ...
in his 1975 book ''
The Mythical Man-Month
''The Mythical Man-Month: Essays on Software Engineering'' is a book on software engineering and project management by Fred Brooks first published in 1975, with subsequent editions in 1982 and 1995. Its central theme is that adding manpower to a s ...
''. According to Brooks, under certain conditions, an incremental person when added to a project makes it take more, not less time.
Explanations
According to Brooks himself, the law is an "outrageous oversimplification",
but it captures the general rule. Brooks points to the main factors that explain why it works this way:
# It takes some time for the people added to a project to become
productive. Brooks calls this the "
ramp up" time. Software projects are complex
engineering
Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...
endeavors, and new workers on the project must first become educated about the work that has preceded them; this education requires diverting resources already working on the project, temporarily diminishing their productivity while the new workers are not yet contributing meaningfully. Each new worker also needs to integrate with a team composed of several engineers who must educate the new worker in their area of expertise in the code base, day by day. In addition to reducing the contribution of experienced workers (because of the need to train), new workers may even make negative contributions, for example, if they introduce bugs that move the project further from completion.
# Communication overhead increases as the number of people increases. Due to
combinatorial explosion
In mathematics, a combinatorial explosion is the rapid growth of the complexity of a problem due to the way its combinatorics depends on input, constraints and bounds. Combinatorial explosion is sometimes used to justify the intractability of cert ...
, the number of different
communication channel
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for infor ...
s increases rapidly with the number of people. Everyone working on the same task needs to keep in sync, so as more people are added they spend more time trying to find out what everyone else is doing.
# Adding more people to a highly divisible task, such as cleaning rooms in a hotel, decreases the overall task duration (up to the point where additional workers get in each other's way). However, other tasks including many specialties in software projects are less divisible; Brooks points out this limited divisibility with another example: while it takes one woman nine months to make one baby, "nine women can't make a baby in one month".
Exceptions and possible solutions
There are some key points in Brooks's law that allow exceptions and open the door for possible solutions.
The first point is to note that Brooks's law only applies to projects that are already late. Projects can be brought back into (or kept in) control if people are added earlier in the process. It is also important to determine if the project is really late, or if the schedule was originally overly optimistic. Scheduling mistakes account for a large number of late projects. Correcting the schedule is the best way to have a meaningful and reliable time frame for the project's completion.
The quantity, quality and role of the people added to the project also must be taken into consideration. One simple way to circumvent the law on an overrun project is to add more people than needed, in such a way that the extra capacity compensates the training and communication overhead. Good
programmer
A programmer, computer programmer or coder is an author of computer source code someone with skill in computer programming.
The professional titles Software development, ''software developer'' and Software engineering, ''software engineer' ...
s or specialists can be added with less overhead for training. People can be added to do other tasks related with the project, for example,
quality assurance
Quality assurance (QA) is the term used in both manufacturing and service industries to describe the systematic efforts taken to assure that the product(s) delivered to customer(s) meet with the contractual and other agreed upon performance, design ...
or documentation; given that the task is clear, ramp up time is minimized.
["The sad but popular approach is to throw people in without much explanation and let everyone figure it out for themselves. But if the manager clarifies why Sally and Rupert are joining, and defines good roles for them, with input from the team, they'll be set up to make a smooth transition." (Berkun, 2006)]
Good
segmentation helps by minimizing the communication overhead between team members. Smaller sub-problems are solved by a smaller team, and a top-level team is responsible for systems integration. For this method to work, the segmentation of the problem must be done correctly in the first place; if done incorrectly, this can make the problem worse, not better, by impeding
communication
Communication is commonly defined as the transmission of information. Its precise definition is disputed and there are disagreements about whether Intention, unintentional or failed transmissions are included and whether communication not onl ...
between programmers working on parts of the problem which are actually closely coupled, even when the project plan has decreed that they are not.
An example of segmentation are
design patterns
''Design Patterns: Elements of Reusable Object-Oriented Software'' (1994) is a software engineering book describing software design patterns. The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a fore ...
that simplify the distribution of work, because the entire team can do its part within the framework provided by that pattern. The design pattern defines the rules that the programmers follow, simplifies communication through the use of a standard language, and provides consistency and scalability.
The Bermuda plan, where most developers on a project are removed ("sent to
Bermuda
Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest.
Bermuda is an ...
") and the remaining are left to complete the software, has been suggested as a way of circumventing Brooks's law.
See also
*
Death march (project management)
*
Anti-pattern
An anti-pattern in software engineering, project management, and business processes is a common response to a recurring problem that is usually ineffective and risks being highly counterproductive. The term, coined in 1995 by computer programmer An ...
*
Linus's law
In software development, Linus's law is the assertion that "given enough eyeballs, all bugs are shallow".
The law was formulated by Eric S. Raymond in his essay and book ''The Cathedral and the Bazaar'' (1999), and was named in honor of Linus To ...
*
List of eponymous laws
*
List of software development philosophies
Notes
References
* Steve McConnell. "Brooks' Law Repealed," IEEE Software, vol. 16, no. 6, pp. 6–8, Nov/Dec, 1999. Also available at the authors website
Brooks's law repealed?.
* Pei Hsia, Chih-tung Hsu, David C. Kung. "Brooks's law Revisited: A System Dynamics Approach," compsac, p. 370, Twenty-Third Annual International Computer Software and Applications Conference, 1999.
* R. L. Gordon and J. C. Lamb. "A Close Look at Brooks' Law," Datamation, June 977, pp. 81–86.
*
Brooks law Is Applicable to Many Collaborative People Activities
{{DEFAULTSORT:Brooks's law
Adages
Computer architecture statements
Computing culture
Software project management
1975 neologisms
Collaboration
Waste of resources