1. What relevance?
Association (association): a class of global variable references another class, it means associated with this class
2, when to use association?
For a long time (to remember) need to be associated retained; do not need a short time. For example:
the need associated with: the teacher taught those courses.
Do not need to associate: Product Description cashier, the cashier does not need to remember which of the inquiry which product.
3. Why should avoid adding a lot of relevance?
In the drawing there are n nodes, inter-node has (n * (. 1-n)) / 2 associations. For example, there are 20 class concept, it will have the largest association line 190. Increased complexity.
Focus "to remember" association.
4, how to draw association?
1 ), class name, the name of association, must be capitalized 2), does not matter whether the arrow, draw many, many to one relationship to
3), the association name, you must verb phrase
The name of the associated format, hump (RecordsCurrent) may also be in horizontal (Records-current)