Attribute declarations have the following format : Attribute « XML Schema « XML Tutorial

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2. XML Schema
3. Attribute

<attribute name="name of the attribute" 
           type="global type" 
           ref="global attribute declaration" 
           form="qualified or unqualified" 
           use="optional or prohibited or required" 
           default="default value" 
           fixed="fixed value"> 

There are two primary methods for declaring attributes: creating a local type or using a global type.

Attribute declarations are restricted to simple types. 
Complex types are used to define types that contain attributes or elements.
Simple types are used to restrict text-only content. 
Because an attribute can contain text only, you can use simple types only to define their allowable content. 
You can reuse attributes by referring to global attribute declarations.