Connection types

Assignments in the content of an element type can occur with varying frequency. The number of permitted occurrences of an assignment in the content of the element type is determined by the connection type between element type and assignment.

The following table explains the various connection types and the corresponding character that is used in the generated DTD to symbolize their occurrence:

Connection type	Description	Character
has any number of times	The assignment must not necessarily occur in the content of the element type being described. It may occur once or multiple times (min = 0, max = any positive integer).	*
has at least once	The assignment must occur in the content of the element type being described and it may occur more than once (min = 1, max = any positive integer).	+
has at most once	The assignment must not necessarily occur in the content of the element type being described. It may occur only once (min = 0, max = 1).	?
has exactly once	The assignment must occur in the content of the element type being described. It may occur only once (min = 1, max = 1).	no character