## 1.2. Notation of a quantifier

The following table describes the explicit forms of a quantifier:

occurs n exactly n occurrences
occurs m..n minimum m occurrences, maximum n occurrences
occurs n..* minimum n occurrences, maximum unlimited

Alternative notations:

occurs required exactly one occurrence (occurs 1)
occurs optional zero or one occurrence (occurs 0..1)
occurs ? zero or one occurrence (occurs 0..1)
occurs * unlimited occurrence (occurs 0..*)
occurs + one or more occurrences (occurs 1..*)

Note since the default value of quantifier is "required" it may
be omitted. E.g.:

` isbn="required int(0, 9999999999)"`
can be written as

`isbn="int(0, 9999999999)"`