XML Schema key Element
 Complete XML Schema Reference
Definition and Usage
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):
- one and only one selector element (contains an XPath expression that
specifies the set of elements across which the values specified by field must
be unique)
- one or more field elements (contains an XPath expression that specifies
the values that must be unique for the set of elements specified by the
selector element)
Element Information
Syntax
<key
id=ID
name=NCName
any attributes
>
(annotation?,(selector,field+))
</key>
|
(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 |
Complete XML Schema Reference
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