The key element specifies an attribute or element value as a key (unique, non-nullable, and always present) within the containing element in an instance document.
The key element MUST contain the following (in order):
(The ? sign declares that the element can occur zero or one time, and the + sign declares that the element must occur one or more times inside the key element)
Attribute | Description |
---|---|
id | Optional. Specifies a unique ID for the element |
name | Required. Specifies the name of the key element |
any attributes | Optional. Specifies any other attributes with non-schema namespace |