`Optionality`

Minimum number of associated records.
Usually 0 or 1
If product must have a supplier, optionality = 1 (Mandatory)
If product might have a supplier, optionality = 0 (Optional)

`Cardinality`

Maximum number of associated records.
Usually 1 or N
If the product can have only one supplier, cardinality = 1
If the product can have multiple supplier, cardinality = N

Optionality and Cardinality are controlled automatically based on constraints.

Relationship	Constraints
`0..1`	NULL + UNIQUE
`1..1`	NOT NULL + UNIQUE
`1..N`	NOT NULL + Not UNIQUE
`0..N`	NULL + Not UNIQUE