Id Assertion The NCName used to declare an attribute MUST NOT be used as the declared NCName of a child element. MAY include the Byte Order Mark (). MUST only contain element nodes and attribute nodes which form a part of one or more complete patterns contained in this specification. MAY contain additional comment nodes and processing instruction nodes. An document conforming to this specification MUST namespace qualify all locally declared elements using a schema element elementFormDefault attribute value of qualified. The xs:schema element MAY be the document element, but MAY also appear within other descriptions such as a or document. An document conforming to this specification MUST define a targetNamespace whose value is an absolute URI. MUST use either the UTF-8 or UTF-16 encoding. MUST be a well-formed document MUST be a 'schema document', as defined in , and MUST therefore meet the "Constraints on the representation of schema components in XML" provided therein.