Page 169 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Unit 13: Class Design

UML Attribute Presentation Notes

The Attribute Presentation recommended by UML is shown as below:
Visibility name: Type – expression = initial – value
Where visibility may be

+ Public visibility
# protected visibility
- Private visibility
Type-expression is a language dependent specification of the implementation type of an attribute.
Initial value is a language-dependent expression for the initial value of a newly created object.

Example: + size: length = 100

Self Assessment

Fill in the blanks:

9. As a ........................., we have to know the specifics of the class we are designing and also we
should be aware of how that class interacts with other classes.
10. ......................... protocols define the functionality and external messages of an object.

11. ......................... protocols define the implementation of an object.
12. In private protocol, only the ......................... itself can use the method.
13. Lack of a well-designed protocol can manifest itself as ......................... leakage.
14. Items in public protocol layer define the ......................... of the object.

15. ......................... attributes can have a collection of several values at a time.
13.3 Summary

An axiom is a fundamental truth that always is observed to be valid and for which there is
no counter example or exception.

A theorem is a proposition that may not be self-evident but can be proved from accepted
axioms.

Corollaries may be called Design rules, and all are derived from the two basic axioms.
Coupling is a measure of the strength of association established by a connection from one
object or software component to another.

Interaction coupling involves the amount and complexity of messages between
components. Inheritance coupling is a form of coupling between super and sub classes.
Object-oriented design requires taking the object identified during object-oriented analysis
and designing classes to represent them.
As a class designer, we have to know the specifics of the class we are designing and also we
should be aware of how that class interacts with other classes.

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