The TemporalDatumBaseType partially defines the origin of a temporal coordinate reference system. This type restricts the AbstractDatumType to remove the "anchorDefinition" and "realizationEpoch" elements.
The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.
Source
<complexType name="TemporalDatumBaseType" abstract="true"><annotation><documentation>The TemporalDatumBaseType partially defines the origin of a temporal coordinate reference system. This type restricts the AbstractDatumType to remove the "anchorDefinition" and "realizationEpoch" elements.</documentation></annotation><complexContent><restriction base="gml:AbstractDatumType"><sequence><element ref="gml:metaDataProperty" minOccurs="0" maxOccurs="unbounded"/><element ref="gml:description" minOccurs="0"/><element ref="gml:descriptionReference" minOccurs="0"/><element ref="gml:identifier"/><element ref="gml:name" minOccurs="0" maxOccurs="unbounded"/><element ref="gml:remarks" minOccurs="0"/><element ref="gml:domainOfValidity" minOccurs="0"/><element ref="gml:scope" maxOccurs="unbounded"/></sequence><attribute ref="gml:id" use="required"/></restriction></complexContent></complexType>