Cardinality

• Cardinality is the specific number of entity occurrences associated with one occurrence of the related entity

• often referred to as ‘business rules’ because cardinality is usually determined by organizational policy

Toy

1

M

e.g., at a toy lending library, a given child may not borrow any toys at all or they may borrow more than one (up to 3) toys. A toy may not be borrowed by anyone, or it may be borrowed by one child.

(0,3)

(0,1)

borrows

Child

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