HOME HTML CSS XML JAVASCRIPT ASP PHP SQL MORE...

Schema Tutorial

XSD HOME
XSD Intro
XSD Why Use
XSD How To
XSD <schema>

Simple Types

XSD Elements
XSD Attributes
XSD Restrictions

Complex Types

XSD Elements
XSD Empty
XSD Elements Only
XSD Text Only
XSD Mixed
XSD Indicators
XSD <any>
XSD <anyAttribute>
XSD Substitution
XSD Example

Data Types

XSD String
XSD Date
XSD Numeric
XSD Misc

XSD Editor
XSD Summary

Schema References

XSD Reference
XSD Validator

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

Parent elements: element

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