A time edge is a one-dimensional topological primitive. It is an open interval that starts and ends at a node. The edge may be realised as a geometry whose value is a time period.
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="TimeEdge" type="gml:TimeEdgeType" substitutionGroup="gml:AbstractTimeTopologyPrimitive"><annotation><documentation>A time edge is a one-dimensional topological primitive. It is an open interval that starts and ends at a node. The edge may be realised as a geometry whose value is a time period.</documentation></annotation></element>