Now I have made decision that I will concentrate more on design. I have to learn more about class design and use case design the things what i have learnt are not enough. Today i have learnt about association, abstraction, composition, aggregation and specialization.
Definitions
Association:- kind of relationship or link between classes. Associations are further documented by stereotypes + roles + multiplicities + constraints + descriptive names + aggregation indicators + navigability indicators. [ uml.coll0.gif ] [ uml.coll1.jpg ] [ uml.game.gif ] [ uml.association.gif ] [ uml.link.gif ]
Composition:- composition::= a strong form of the 'has_a' or APO relation so that deleting the whole automatically removes the parts as well. Composition fits when objects of one class are made up of parts that are objects of other classes, for example when they are implemented using fields in structures, items in records, columns in a data base, or pieces of a document. However, in some cases, the responsibility for keeping an object alive changes during that objects life, and so that objects class would be shown as being parts of several different compositions. [ clock2.gif ] [ uml.period.gif ] [ uml.link.gif ]
Aggregation: - aggregation::=a way that one class can refer to another class without having possession of it + a weak form of 'has-a' / APO link + if the whole object is an aggregation then deleting it does not effect the existence of the aggregated part. An open diamond at one end of a link shows this relationship. The other end may have an arrowhead indicating the link can be navigated in one direction only.
Specialization:- When we derive a class from an existing class and add some functionality to it becomes a specialization
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