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.