title: How do I specify a constant attribute in XML Schema?
body: <p>Reading over the <a href="http://www.w3.org/XML/Schema" rel="noreferrer">XML Schema</a> specification, I can't see an easy way to mark an attribute as being constant (e.g. in <code>&lt;foo bar="baz" /&gt;</code> the <code>bar</code> attribute must always be <code>baz</code>).  The only method I have come up with so far is to use an enumeration with only one element.  Is this the preferred method?</p>