Inside XML

Specifying Attribute Constraints and Defaults

As with elements, you can specify the type of attributes. Unlike with elements, however, attributes must be of a simple type. In addition, you don't use minOccurs and maxOccurs for attributes because attributes can appear only once, at most. Instead, you use a different syntax when constraining attributes.

You declare attributes with the <xsd:attribute> element. The <xsd:attribute> element itself has a type attribute that gives the attribute's (simple) type. So how do you indicate if an attribute is required or optional, or if there's a default value, or even if the value of the attribute is fixed at a certain value? You use the <xsd:attribute> element's use and value attributes.

The use attribute ...