XML Schema key element

Definition and Usage

key elements of the specified attribute or element value (or set of values) must be a key within the specified range. Key range for instance document contains element. Key means that the data in the specified range should be unique, non-zero and is always present.

key element must contain the following elements in order:

• selector element contains an XPath expression that specifies a set of elements, the elements are concentrated, the value of the specified field must be unique.

Element Information

• Parent element: element

grammar

(? Sign declares that the key element, the element can occur zero or one time, the + sign declares that the element must occur one or more times.)