Time and Requisite Variety:
Lessons from Project Management
Frank T. Anbari and Stuart A. Umpleby
The George Washington University
Washington, DC
The law of requisite variety
• First described by W. Ross Ashby in 1952
• Similar to game theory – have a move to
counter every possible move by an
opponent
• Time is a separate dimension not included
when calculating variety
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First version
• The amount of selection that can be
performed is limited by the amount of
information available
• Example: Admitting students to college
• What if there are five students and
information on only three?
• “When all available information has been
exhausted, do whatever you like.”
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Second version
• The variety in the regulator must be at least
as great as the variety in the system being
regulated
• Example: Buy a computer with a capacity
not less than the required task
• Example: In sports have a defense for every
offense and seek to create novel offenses
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Implication for management
• When confronted with a task more
complicated than one can cope with, there
are two and only two choices
• One: Increase the variety in the regulator
(for example by hiring more staff)
• Two: Reduce the variety in the system
being regulated
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Implementing the second strategy
• The second strategy is surprisingly powerful
• Reducing the variety in the system being
regulated is possible because a system is “a
set of variables defined by the observer”
• That is, one can redefine the system so that
it is manageable
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Projects and Programs
• “A project is a temporary endeavor
undertaken to create a unique product,
service, or result…Most projects are
undertaken to create a lasting outcome.”
• “A program is a group of related projects
managed in a coordinated way to obtain
benefits and control not available from
managing them individually.”
Project Management Institute (2004)
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Rich, Long History of
Project Management (PM)
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The Wheel
The Pyramids
The Great Walls of China
Roads, viaducts, Canals, and architecture
Defense systems
Computers and telecommunications
Medical and pharmaceutical projects
Space exploration and utilization
Sources: Cleland, David I. The Societal Contribution of Project Management, IPMA 17th World Congress on
Project Management, Moscow, Russia June 4-6, 2003, and Anbari, F.T. & Romanova, M.V. Developing
Competitive Organizations trough Six Sigma, Innovation, and Project Management, EURO / INFORMS
Joint International Meeting, Istanbul, Turkey, July 6-10, 2003.
Continued…
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Projects and Project Management
• A project can be defined as a system that
transforms inputs into outputs and has a
feedback mechanism:
 The system to be regulated
• The PM system (including the project
manager and team) can be defined as:
 The regulator
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A Systems Approach to Project Management
INPUT
Physical
Human
Conceptual
PROCESS
Integration
Scope
Time
Cost
Quality
Human Resources
Communications
Procurement
Risk
OUTPUT
Physical
Conceptual
Scope
Time
Cost
Quality
FEEDBACK
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Projects as Systems
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Projects are Complex systems
May have a single or often multiple objectives
The objectives may have different priorities
Highly constrained usually with multiple
constraints
• Some objectives may also act as constraints
• Systems dynamics and interventions by key
stakeholders increase complexity of the project
management system
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Project objectives and constraints
• Time and cost have traditionally been considered
as the main constraints on projects
• The triple constraint theory adds a third constraint
(often called performance)
• Scope, time, cost, and quality have been proposed
as the quadruple objectives and constraints
• Risk tolerance and resource availability may be
added as constraints only
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Quadruple Objectives / Constraints of
Project Management
Scope
Quality
Time
Cost
With proper
prioritization of
project objectives
F. T. Anbari, 1985, 2005
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Prioritization of objectives: Example
Priority
Scope
Time
Cost
Quality
First
Second
Third
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Time and requisite variety
• Previously in discussions of requisite variety, time
was not considered because it was thought to be a
different kind of variable
• In the game theoretical formulation, requisite
variety lists capabilities, which are executed in time
• However, time is itself a capability or is a way to
increase capability
• This is a notion that was excluded in the original,
formal, game theoretical interpretation of requisite
variety
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Time in project management
• In managing projects, time is usually considered to
be a critical (trade-off) variable:
– Taking more time often allows projects to be completed
to satisfy other project objectives
– The time constraint often affects the achievement of
other project objectives
• The common practice of "extending time" in
project management calls attention to the formal
interpretation of time in the cybernetics literature
• A broader interpretation of time can bring
cybernetics closer to other fields
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The Correspondence Principle
• Proposed by Niels Bohr when developing
quantum theory
• Any new theory should reduce to the old
theory to which it corresponds for those
cases in which the old theory is known to
hold
• A new dimension is required
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“New” Law of requisite variety
Law of requisite variety
Time variable
An Application of the Correspondence Principle
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The law of requisite variety and
project management
• The law of requisite variety can make
important contributions to PM, since the
PM system (or process) approach is
becoming very widely accepted in PM
• PM can make an interesting contribution to
cybernetics and the law of requisite
variety by appropriately addressing the time
variable
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Cybernetics and behavioral science
• An advantage of cybernetics is that it
sometimes lends itself to mathematical
analysis, similar to game theory
• Most of behavioral science is not expressed
as axiomatic theories:
– Behavior occurs in time
• Including time with requisite variety may
lead to analyses closer to behavioral science
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References
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Anbari, F. T. (1985). “A Systems Approach to Project Evaluation,” Project Management Journal,
Vol. XVI, No. 3, pp. 21 – 26.
Anbari, F. T. (2005). Innovation, Project Management, and Six Sigma Method. Current Topics in
Management, Vol. 10, pp. 101-116, New Brunswick, NJ: Transaction Publishers
Ashby, W. R. (1952). Design for a Brain: The Origin of Adaptive Behavior. London: Chapman and
Hall.
Ashby, W. R. (1957). An Introduction to Cybernetics. London: Chapman and Hall.
Checkland, P. (2000). Soft Systems Methodology: A Thirty Year Retrospective. Systems Research
and Behavioral Science, Vol. 17, Iss. S1, pp. S11 – S58.
Schwaninger, M. (2004). What can cybernetics contribute to the conscious evolution of organizations
and society? Systems Research and Behavioral Science, Vol. 21, Iss. 5, pp. 515 – 527.
Project Management Institute. (2004). A guide to the project management body of knowledge, (3rd
ed.). Newtown Square, PA: Author.
Umpleby, S.A. (2004). “Strategies for Regulating the Global Economy.” Cybernetics and Systems.
Retrieved on October 22, 2005 from http://www.gwu.edu/~umpleby/recent_papers/st_regulating.htm
Umpleby, S. A. (2002). Should Knowledge of Management Be Organized as Theories or as
Methods? The George Washington University. Retrieved on July 28, 2005 from
http://www.gwu.edu/~umpleby/recent_papers/2002_knowledge_of_management_organized_as_theor
ies_or_as_methods.htm
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