This schema defines attributes and an attribute group suitable

　　for use by schemas wishing to allow ,

　　, or

　　attributes on elements they define.

　　To enable this, such a schema must import this schema for

　　the XML namespace, e.g. as follows:

　　. . .

　　schemaLocation="http://www.w3.org/2001/xml.xsd"/>

　　or

　　schemaLocation="http://www.w3.org/2009/01/xml.xsd"/>

　　Subsequently, qualified reference to any of the attributes or the

　　group defined below will have the desired effect, e.g.

　　. . .

　　will define a type which will schema-validate an instance element

　　with any of those attributes.