CS 696: Advanced OO
Spring Semester, 1997
Doc 4, Cohesion part 2

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San Diego State University -- This page last updated Feb 10, 1997

Cohesion 2

References

Object Coupling and Object Cohesion, chapter 7 of Essays on Object-Oriented Software Engineering, Vol 1, Berard, Prentice-Hall, 1993,

Doc 4, Cohesion part 2 Slide # 1

A composite object is an object that is conceptually composed of two, or more, other objects, which are externally discernable.

Component objects are those that make up the composite object.

Component objects are externally discernable if

component objects can be directly queried or changed via methods in the public interface of the composite object and/or
the externally discernible state of the object is directly affected by the presence or absence of one or more component objects

Doc 4, Cohesion part 2 Slide # 2
Ranking of Cohesion of Composite Objects
Increasing Order of Goodness

externally discernible component objects not related
some externally discernible component objects are related, the group component objects does not make sense
the group component objects does not represent a single stable object-oriented concept, but are all bound together some how in an application
a majaroity of the externally discernible component objects support a single,coherent, object-oriented concept, but at least one does not
all of the externally discernible component objects support a single,coherent, object-oriented concept, but at least one needed object is missing
all of the externally discernible component objects support a single,coherent, object-oriented concept, and none are missing

Doc 4, Cohesion part 2 Slide # 3

Accessing Cohesion of an Individual Object

Accessment of the public methods/public non methods/component objects