Element schemaRoot = doc.addElement("xsd:schema", W3C_XML_SCHEMA_NS_URI);
schemaRoot.addNamespace("xsd", W3C_XML_SCHEMA_NS_URI);
schemaRoot.addNamespace("beans", BEANS_NAMESPACE_URI);
schemaRoot.addNamespace("springext", SPRINGEXT_BASE_URI);
schemaRoot.addNamespace("", configurationPoint.getNamespaceUri());
schemaRoot.addAttribute("targetNamespace", configurationPoint.getNamespaceUri());
// <xsd:include schemaLocation="contribution schema" />
Set<String> includings = createTreeSet();