Information Technology Reference
In-Depth Information
Fig. 7.3
Top down design
DrawableObject
MultiPointObject
TwoPointObject
Polygon
Curve
Line
Rectangle
Oval
detailed system design. Object-oriented design has led to object-oriented approach
in the software world.
7.6 Object-Oriented Design Concepts
Object-oriented design intuitively revolves around the specification and elicitation
of objects. The purpose of OOD is not only to determine what objects are needed,
but the methods and attributes of these objects. Relationships between the objects
also must be determined, and in some manner documented. This documentation,
even though it is not intended to be executed by a computer, must be capable of
human understanding.
7.6.1 Abstractions
A model is essentially an abstraction of the real world. It captures only the
essential and relevant characteristics of the real world (Jia
2003
). Abstraction
should lead to the development of models. These models should be able to mimic
the behavior and form of the physical world when implemented. Just like the real
world understanding of an entity, an abstraction can only maintain a portion of the
actual information concerning the entity. For example, if you were to abstract a
chair (the common ordinary dining room table type) into a class you very easily
could come up with attributes such as height, weight, color, if it can swivel, the
material it is made out of etc. This may sound like a perfectly complete, including
any other items you may realized were missing from my list. Yet, there are many
more items that could be added to both our lists; where the raw materials origi-
nated, density, age, manufacturer and how much dust resides on it. The list could
go on forever and that is why only the important aspects of the chair (or anything
else) should be included in the abstraction.
