Page 21 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Unit 2: Modelling Concepts

Self Assessment Notes

Fill in the blanks:
1. ....................... looks at the problem domain, with the aim of producing a conceptual model
of the information that exists in the area being analyzed.

2. ....................... elaborates the analysis models to produce implementation specifications.
3. The concepts in the ....................... model are mapped onto implementation classes and
interfaces.

2.2 Modelling

In this section, we will discuss the concept of modelling.

2.2.1 Definition of Modelling

A model is an abstraction of something for the purpose of understanding it before building it.
Because, real systems that we want to study are generally very complex. In order to understand
the real system, we have to simplify the system. So a model is an abstraction that hides the
non-essential characteristics of a system and highlights those characteristics, which are pertinent
to understand it. Efraim Turban describes a model as a simplified representation of reality. A
model provides a means for conceptualization and communication of ideas in a precise and
unambiguous form. The characteristics of simplification and representation are difficult to achieve
in the real world, since they frequently contradict each other. Thus modeling enables us to cope
with the complexity of a system.
Most modeling techniques used for analysis and design involve graphic languages. These graphic
languages are made up of sets of symbols. As you know one small line is worth thousand words.
So, the symbols are used according to certain rules of methodology for communicating the
complex relationships of information more clearly than descriptive text.
Modeling is used frequently, during many of the phases of the software life cycle such as
analysis, design and implementation. Modeling like any other object-oriented development, is
an iterative process. As the model progresses from analysis to implementation, more detail is
added to it.

2.2.2 Why do we Model?

Before constructing anything, a designer first build a model. The main reasons for constructing
models include:

To test a physical entity before actually building it.
To set the stage for communication between customers and developers.
For visualization i.e. for finding alternative representations.
For reduction of complexity in order to understand it.

2.2.3 Object-oriented Modelling (OOM)

Object oriented modeling is entirely a new way of thinking about problems. This methodology
is all about visualizing the things by using models organized around real world concepts.
Object oriented models help in understanding problems, communicating with experts from a

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