gml:TimeGeometricPrimitive acts as the head of a substitution group for geometric temporal primitives.A temporal geometry shall be associated with a temporal reference system through the frame attribute that provides a URI reference that identifies a description of the reference system. Following ISO 19108, the Gregorian calendar with UTC is the default reference system, but others may also be used. The GPS calendar is an alternative reference systems in common use.The two geometric primitives in the temporal dimension are the instant and the period. GML components are defined to support these as follows.
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
<element name="AbstractTimeGeometricPrimitive" type="gml:AbstractTimeGeometricPrimitiveType" abstract="true" substitutionGroup="gml:AbstractTimePrimitive"><annotation><documentation>gml:TimeGeometricPrimitive acts as the head of a substitution group for geometric temporal primitives. A temporal geometry shall be associated with a temporal reference system through the frame attribute that provides a URI reference that identifies a description of the reference system. Following ISO 19108, the Gregorian calendar with UTC is the default reference system, but others may also be used. The GPS calendar is an alternative reference systems in common use. The two geometric primitives in the temporal dimension are the instant and the period. GML components are defined to support these as follows.</documentation></annotation></element>