UMLDI — di-schema.xsd

The di-schema.xsd available from the link http://www.omg.org/cgi-bin/doc?ptc/05-06-07 import namespace <xsd:import namespace="http://www.omg.org/XMI" schemaLocation="XMI.xsd"/>. XMI.xsd is not present in the same package throws schema error on di-schema.xsd. Where can be the approved XMI.xsd found that the di-schema refers to.