nYou
can think of the type itself as the
set of strings/EIIs its constraints allow. It's helpful to think of constraints as composed of obligations and
permissions:
ä (\d )?(\d{3}-)?\d{3}-\d{4}
äregexp
definition facet for [US] 'phone number type
n the ? and the \d can be seen as permissions,
the -
and the {3} as obligations
ä 1 337-6818 and 207-422-6240 belong to this
type
