In the Summer 14 (v31.0) of the Metadata API complex types are added for CustomMetadata and CustomMetadataValue. The latter appears in the values element of the former. CustomMetadata extends Metadata, as do another 98 other complex types.
What are these new types for and how do I use them?
I can't find them in the documented Metadata types.
Extract from the WSDL:
<xsd:complexType name="CustomMetadata">
<xsd:complexContent>
<xsd:extension base="tns:Metadata">
<xsd:sequence>
<xsd:element name="description" minOccurs="0" type="xsd:string"/>
<xsd:element name="label" minOccurs="0" type="xsd:string"/>
<xsd:element name="values" minOccurs="0" maxOccurs="unbounded" type="tns:CustomMetadataValue"/>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:complexType name="CustomMetadataValue">
<xsd:sequence>
<xsd:element name="field" type="xsd:string"/>
<xsd:element name="value" type="xsd:anyType"/>
</xsd:sequence>
</xsd:complexType>