Creating a Local/Global Type for Attribute : Attribute « XML Schema « XML Tutorial

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3. Attribute

To create a local type, simply include the type declaration as a child of the <attribute> element: 

<attribute name="title"> 
    <simpleType> 
        <!-- type information --> 
    </simpleType> 
</attribute> 

Using a Global Type for Attribute

You can create a global <simpleType> definition. 
Within your attribute declarations, you can refer to a global type by name. 
This type can be one of the built-in XML Schema datatypes.
Referring to an Existing Global Attribute 

<attribute ref="contacts:kind"/>