<p>
This schema defines attributes and an attribute group suitable
for use by schemas wishing to allow
<code>xml:base</code>
,
<code>xml:lang</code>
,
<code>xml:space</code>
or
<code>xml:id</code>
attributes on elements they define.
</p>
<p>
To enable this, such a schema must import this schema for
the XML namespace, e.g. as follows:
</p>
<pre>
<schema . . .>
. . .
<import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd"/>
</pre>
<p>
or
</p>
<pre>
<import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2009/01/xml.xsd"/>
</pre>
<p>
Subsequently, qualified reference to any of the attributes or the
group defined below will have the desired effect, e.g.
</p>
<pre>
<type . . .>
. . .
<attributeGroup ref="xml:specialAttrs"/>
</pre>
<p>
will define a type which will schema-validate an instance element
with any of those attributes.
</p>