Attempting to install the relevant ISO 2- and 3-letter codes as the enumerated possible values is probably never going to be a realistic possibility. See RFC 3066 at http://www.ietf.org/rfc/rfc3066.txt and the IANA registry at http://www.iana.org/assignments/lang-tag-apps.htm for further information. The union allows for the 'un-declaration' of xml:lang with the empty string.
Source
<xs:element name="packageItem"><xs:annotation><xs:documentation>An Item used for packaging references to other Items and Web resources.</xs:documentation></xs:annotation><xs:complexType><xs:complexContent><xs:extension base="AnyItemType"><xs:sequence><xs:element name="contentMeta" minOccurs="0"><xs:annotation><xs:documentation>A set of properties about the content</xs:documentation></xs:annotation><xs:complexType><xs:sequence><xs:element ref="icon" minOccurs="0"/><xs:group ref="AdministrativeMetadataGroup"/><xs:group ref="DescriptiveMetadataGroup" minOccurs="0"/><xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/></xs:sequence><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element><xs:element name="groupSet" minOccurs="0"><xs:annotation><xs:documentation>A hierarchical set of groups</xs:documentation></xs:annotation><xs:complexType><xs:sequence><xs:element name="group" maxOccurs="unbounded"><xs:annotation><xs:documentation>A mixed set of group references and links</xs:documentation></xs:annotation><xs:complexType><xs:choice minOccurs="0" maxOccurs="unbounded"><xs:element name="groupRef"><xs:annotation><xs:documentation>A reference to a group local to the package</xs:documentation></xs:annotation><xs:complexType><xs:attribute name="idref" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to the id of a local group</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element><xs:element name="itemRef" type="LinkType"><xs:annotation><xs:documentation>A reference to a target item or Web resource</xs:documentation></xs:annotation></xs:element></xs:choice><xs:attribute name="id" type="xs:ID" use="required"><xs:annotation><xs:documentation>The local identifier of the group</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="role" type="QCodeType" use="required"><xs:annotation><xs:documentation>The part this group plays within its container</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="mode" type="QCodeType"><xs:annotation><xs:documentation>An indication whether the elements in the group are complementary and unordered, complementary and ordered or a set of alternative elements</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element></xs:sequence><xs:attribute name="root" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to a local group acting as the root of the hierarchy of groups</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element></xs:sequence></xs:extension></xs:complexContent></xs:complexType></xs:element>
ANY attribute from ANY namespace OTHER than 'http://iptc.org/std/nar/2006-10-01/'
Source
<xs:element name="contentMeta" minOccurs="0"><xs:annotation><xs:documentation>A set of properties about the content</xs:documentation></xs:annotation><xs:complexType><xs:sequence><xs:element ref="icon" minOccurs="0"/><xs:group ref="AdministrativeMetadataGroup"/><xs:group ref="DescriptiveMetadataGroup" minOccurs="0"/><xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/></xs:sequence><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element>
The reference to a local group acting as the root of the hierarchy of groups
Source
<xs:element name="groupSet" minOccurs="0"><xs:annotation><xs:documentation>A hierarchical set of groups</xs:documentation></xs:annotation><xs:complexType><xs:sequence><xs:element name="group" maxOccurs="unbounded"><xs:annotation><xs:documentation>A mixed set of group references and links</xs:documentation></xs:annotation><xs:complexType><xs:choice minOccurs="0" maxOccurs="unbounded"><xs:element name="groupRef"><xs:annotation><xs:documentation>A reference to a group local to the package</xs:documentation></xs:annotation><xs:complexType><xs:attribute name="idref" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to the id of a local group</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element><xs:element name="itemRef" type="LinkType"><xs:annotation><xs:documentation>A reference to a target item or Web resource</xs:documentation></xs:annotation></xs:element></xs:choice><xs:attribute name="id" type="xs:ID" use="required"><xs:annotation><xs:documentation>The local identifier of the group</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="role" type="QCodeType" use="required"><xs:annotation><xs:documentation>The part this group plays within its container</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="mode" type="QCodeType"><xs:annotation><xs:documentation>An indication whether the elements in the group are complementary and unordered, complementary and ordered or a set of alternative elements</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element></xs:sequence><xs:attribute name="root" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to a local group acting as the root of the hierarchy of groups</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element>
<xs:element name="group" maxOccurs="unbounded"><xs:annotation><xs:documentation>A mixed set of group references and links</xs:documentation></xs:annotation><xs:complexType><xs:choice minOccurs="0" maxOccurs="unbounded"><xs:element name="groupRef"><xs:annotation><xs:documentation>A reference to a group local to the package</xs:documentation></xs:annotation><xs:complexType><xs:attribute name="idref" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to the id of a local group</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element><xs:element name="itemRef" type="LinkType"><xs:annotation><xs:documentation>A reference to a target item or Web resource</xs:documentation></xs:annotation></xs:element></xs:choice><xs:attribute name="id" type="xs:ID" use="required"><xs:annotation><xs:documentation>The local identifier of the group</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="role" type="QCodeType" use="required"><xs:annotation><xs:documentation>The part this group plays within its container</xs:documentation></xs:annotation></xs:attribute><xs:attribute name="mode" type="QCodeType"><xs:annotation><xs:documentation>An indication whether the elements in the group are complementary and unordered, complementary and ordered or a set of alternative elements</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element>
<xs:element name="groupRef"><xs:annotation><xs:documentation>A reference to a group local to the package</xs:documentation></xs:annotation><xs:complexType><xs:attribute name="idref" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to the id of a local group</xs:documentation></xs:annotation></xs:attribute><xs:anyAttribute namespace="##other" processContents="lax"/></xs:complexType></xs:element>
The version of the target resource. By default, the latest revision is retrieved when the link is activated.
Source
<xs:element name="itemRef" type="LinkType"><xs:annotation><xs:documentation>A reference to a target item or Web resource</xs:documentation></xs:annotation></xs:element>
<xs:attribute name="idref" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to the id of a local group</xs:documentation></xs:annotation></xs:attribute>
<xs:attribute name="id" type="xs:ID" use="required"><xs:annotation><xs:documentation>The local identifier of the group</xs:documentation></xs:annotation></xs:attribute>
<xs:attribute name="role" type="QCodeType" use="required"><xs:annotation><xs:documentation>The part this group plays within its container</xs:documentation></xs:annotation></xs:attribute>
<xs:attribute name="mode" type="QCodeType"><xs:annotation><xs:documentation>An indication whether the elements in the group are complementary and unordered, complementary and ordered or a set of alternative elements</xs:documentation></xs:annotation></xs:attribute>
<xs:attribute name="root" type="xs:IDREF" use="required"><xs:annotation><xs:documentation>The reference to a local group acting as the root of the hierarchy of groups</xs:documentation></xs:annotation></xs:attribute>