Operations Research An Introduction 160906031603
Operations Research An Introduction 160906031603
Operations Research An Introduction 160906031603
Extensions
Modeling Using
New Theories Unification Existing Models
Constructing
Hypothesis
Orientation
Problem Definition
Validation and Output Analysis
Solution
Implementation and Monitoring
Data Collection
Model Formulation
Basis of Classification
Descriptive Normative
Model Model
Predictive
Model Static Dynamic Analytical Simulation
Physical Symbolic Model Model Model Model Model
Model Model
under study either reduced in size or scaled up. These models cannot be
manipulated and not very useful for prediction, therefore, problems such as
portfolio section, media selection, production scheduling, etc. cannot be analysed
with a physical model. Physical models are classified into the following two
categories.
Iconic Models : Iconic models retain some of the physical and characteristics of the
system they represent. An iconic model is either in an idealized form or a scaled
version of the system. It is said to be scaled down when the dimensions of the
model are smaller than those of the real object and model said to be scaled up
when it is bigger than the real object. In other words, it is an image.
Examples :
A globe representing the earth.
Blue prints of a home.
Model of a cell in biology.
A baby toy car as a model of an automobile.
PHYSICAL MODELS
Analogue Model: These models represent a system or object by using set of
properties different from the ones, held by the original object or system.
There is no ‘look-alike’ relation between the model and the original. i.e.
These models represent a system by the set of properties different from that
of the original system and does not resemble physically. After the problem is
solved, the solution is re-interpreted in terms of the original system.
Example :
Organizational chart represent the state of formal relationships existing between
members of the organization.
Maps in different colours may represent water, desert, mountains etc.
Graphs of time series, stock market etc. may be used to represent quantitative
relationship between any two properties.
Both models are easier to manipulate and can represent dynamic situations; so
analogue model is more popular than iconic models.
SYMBOLIC MODELS
These models use symbols like letters, numbers etc.to represent the
properties of the system. These models are also used to
represent relationships which can be represented in a physical
form. Symbolic models can be classified into two categories:
Verbal Models: These models describe a situation in written or
spoken language.
Example: Written sentences, books, newspapers, journals etc.
Mathematical Models: These models represent the characteristics
of a situation or reality by using a set of mathematical symbols
and relationships. These models are widely used in OR due to
their capacity to depict the complex relationship among the
variables of a problem. Example : ‘+’, ‘–‘, ‘×’, ‘÷’.
CLASSIFICATION BASED ON PURPOSE
The models based on the purpose of their utility include :
Descriptive Models: Descriptive models simply describe some features of a situation based on observation
survey or other available data of a situation and do not predict or recommend.
Example :
Result of a n opinion poll.
Block diagram representing an algorithm or method for solving a problem.
Predictive Models: These models indicate that ‘if this occurs then that will follow’. They related dependent
and independent variables and permit trying out, ‘what if’ questions. In other words, these models are
used to predict the outcomes due to a given set of alternatives for the problem.
Example :
Television network try to predict the election results before the counting of all the votes.
Rain forecast before actual rainfall.
Normative Models : When a model has been repeatedly successful, it can be used to develop objective
decision rules or criteria for optimal solutions. These models are applicable to repetitive problems.
Example :
Linear programming is a normative or prescriptive model, because it prescribes what the managers
should do.
CLASSIFICATION BASED ON BEHAVIOUR