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Written by Sleepy Egg
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Monday, 04 July 2005 |
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Class diagram describes the relationships between classes. A Class is type of an instance object. Instance object of a specific class will follow the behaviors we have set for that class. That is OOP, baby!
There are many types relationships that a class can have with other classes. These relationships are guarded by rules. Rule can be a set of standard rules or user specified rules. Lets talk about relationships guarded by set of standard rules:
1. Association
2. Aggregation (Association + more rules)
3. Compostion (Aggregation + more rules)
Exaple of Association:
'a customer places an order.'
customer is a type of object (class).
order is another type of object
place order is an 'action' that creates an relationship (link) betwen the two classes.
Rules:
1. How many orders can a customer place? Rule says: 0 to infinite
1. Can an order be placed by how many customers? Rule says: 1 and only 1 [>:)'>
Now here is the clasess with summarized rules:
customer (1..1) -------place order ------- (0..infinite) order
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