Following seven rules control how the elements are used in terms of their sequence, number of occurrences, and group.
Indicates that child elements can appear in any sequence but must appear at least once.
Indicates one or the other child element can occur.
Indicates the order in which the child elements appear.
Indicates the minimum number of times a child element can occur.
Indicates the maximum number of times a child element can occur.
Elements can be grouped under a group declaration.
Attributes can be grouped under an attributeGroup declaration.