6.3.6 Enlarging the Paradigm
During the past decades, many attempts have been made to enlarge the system
dynamics paradigm by including appropriate tools and techniques from other fields
of inquiry. The following paragraphs touch upon these new links.
(a) Operations research
Operations research basically helps in finding out values of decision variables
which optimize quantitative objective functions under constraints. An operations
research model usually operates in an open loop manner. The emphasis is normally
on isolated decision(s) at discrete time points. The short planning horizon usually
used in an operations research approach, the urgency of the problem which it
addresses, and the immediacy of results which it can render upon implementation
makes it very attractive to practitioners.
Table 6.2 Problem-solving stages and the associated viewpoints
Stages
Viewpoints
1 Define the problem
Models try to solve problems
The models aim at solving long-term problems
The central focus is policy
2 Define the model boundary and
build model aggregate.
Cause-effect links play a major role
Policy decisions appear in feedback loops
Behaviour is generated endogenously
3 Build the detailed model
A mental database is used to construct causal structures
It explicitly considers physical and information flows
Most models are generic in nature
Policy structures are expected to hold under all
conditions
It uses simple graphical and mathematical schemes
The model emphasizes more on the structure rather
than on the values of the variables
In real life, decision variables are not always continuous, but the model may simplify
4 Test and validate the model
The model should simulate symptoms of problems
encountered with real systems
Model validation is a multi-stage procedure
The model is tested under extreme conditions
5 Analyse the model and evaluate the
policy alternatives
Model understanding is the basis for deriving new
model or policy structures
New policies are intuitively developed.
Causal structures generating past behaviour do not
change substantially in the future
6 Recommend the most viable policy The dynamics of implementation of the new policies
can also be modelled
166
6 Infrastructure as a System
During the past decades, many attempts have been made to enlarge the system
dynamics paradigm by including appropriate tools and techniques from other fields
of inquiry. The following paragraphs touch upon these new links.
(a) Operations research
Operations research basically helps in finding out values of decision variables
which optimize quantitative objective functions under constraints. An operations
research model usually operates in an open loop manner. The emphasis is normally
on isolated decision(s) at discrete time points. The short planning horizon usually
used in an operations research approach, the urgency of the problem which it
addresses, and the immediacy of results which it can render upon implementation
makes it very attractive to practitioners.
Table 6.2 Problem-solving stages and the associated viewpoints
Stages
Viewpoints
1 Define the problem
Models try to solve problems
The models aim at solving long-term problems
The central focus is policy
2 Define the model boundary and
build model aggregate.
Cause-effect links play a major role
Policy decisions appear in feedback loops
Behaviour is generated endogenously
3 Build the detailed model
A mental database is used to construct causal structures
It explicitly considers physical and information flows
Most models are generic in nature
Policy structures are expected to hold under all
conditions
It uses simple graphical and mathematical schemes
The model emphasizes more on the structure rather
than on the values of the variables
In real life, decision variables are not always continuous, but the model may simplify
4 Test and validate the model
The model should simulate symptoms of problems
encountered with real systems
Model validation is a multi-stage procedure
The model is tested under extreme conditions
5 Analyse the model and evaluate the
policy alternatives
Model understanding is the basis for deriving new
model or policy structures
New policies are intuitively developed.
Causal structures generating past behaviour do not
change substantially in the future
6 Recommend the most viable policy The dynamics of implementation of the new policies
can also be modelled
166
6 Infrastructure as a System