TimeTopologyPrimitivePropertyType TimeTopologyComplex Temporal topology objects .1 Overview

160 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. extension complexContent complexType A temporal topology complex is a set of connected temporal topology primitives. The member primitives are indicated, either by reference or by value, using the gml:primitive property.

14.3.2.5 TimeTopologyComplexPropertyType

gml:TimeTopologyComplexPropertyType provides for associating a gml:TimeTopologyComplex with an object: complexType name=TimeTopologyComplexPropertyType sequence minOccurs=0 element ref=gml:TimeTopologyComplex sequence attributeGroup ref=gml:AssociationAttributeGroup attributeGroup ref=gml:OwnershipAttributeGroup complexType

14.3.2.6 TimeNode

A time node is a zero-dimensional topology primitive that represents an identifiable node in time it is equivalent to a point in space. A node may act as the termination or initiation of any number of time edges. A time node may be realized as a geometry, its position, whose value is a time instant. gml:TimeNode implements ISO 19108 TM_Node see D.2.5.6 and ISO 19108:2002, 5.2.4.3 and is declared as follows: element name=TimeNode type=gml:TimeNodeType substitutionGroup=gml:AbstractTimeTopologyPrimitive gml:TimeNode may be used in any position that a gml:AbstractTimeTopologyPrimitive is valid. Its content model is defined as follows: complexType name=TimeNodeType complexContent extension base=gml:AbstractTimeTopologyPrimitiveType sequence element name=previousEdge type=gml:TimeEdgePropertyType minOccurs=0 maxOccurs=unbounded element name=nextEdge type=gml:TimeEdgePropertyType minOccurs=0 maxOccurs=unbounded element name=position type=gml:TimeInstantPropertyType minOccurs=0 sequence extension complexContent complexType

14.3.2.7 TimeNodePropertyType

gml:TimeNodePropertyType provides for associating a gml:TimeNode with an object: complexType name=TimeNodePropertyType sequence minOccurs=0 element ref=gml:TimeNode sequence attributeGroup ref=gml:AssociationAttributeGroup attributeGroup ref=gml:OwnershipAttributeGroup complexType Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 161

14.3.2.8 TimeEdge

A time edge is a one-dimensional topology primitive. It is an open interval that starts and ends at a node. The edge may be realized as a geometry whose value is a time period. gml:TimeEdge implements ISO 19108 TM_Edge see D.2.5.6 and ISO 19108:2002, 5.2.4.4 and is declared as follows: element name=TimeEdge type=gml:TimeEdgeType substitutionGroup=gml:AbstractTimeTopologyPrimitive gml:TimeEdge may be used in any position that a gml:AbstractTimeTopologyPrimitive is valid. Its content model is defined as follows: complexType name=TimeEdgeType complexContent extension base=gml:AbstractTimeTopologyPrimitiveType sequence element name=start type=gml:TimeNodePropertyType element name=end type=gml:TimeNodePropertyType element name=extent type=gml:TimePeriodPropertyType minOccurs=0 sequence extension complexContent complexType

14.3.2.9 TimeEdgePropertyType

gml:TimeEdgePropertyType provides for associating a gml:TimeEdge with an object: complexType name=TimeEdgePropertyType sequence minOccurs=0 element ref=gml:TimeEdge sequence attributeGroup ref=gml:AssociationAttributeGroup attributeGroup ref=gml:OwnershipAttributeGroup complexType

14.4 Temporal reference systems

14.4.1 Overview

A value in the time domain is measured relative to a temporal reference system. Common types of reference system include calendars, ordinal temporal reference systems, and temporal coordinate systems time elapsed since some epoch. The primary temporal reference system for use with geographic information is the Gregorian Calendar and 24 hour local or Coordinated Universal Time UTC, but special applications may entail the use of alternative reference systems. The Julian day numbering system is a temporal coordinate system that has an origin earlier than any known calendar, at noon on 1 January 4713 BC in the Julian proleptic calendar, and is useful in transformations between dates in different calendars. In GML seven concrete elements are used to describe temporal reference systems: gml:TimeReferenceSystem, gml:TimeCoordinateSystem, gml:TimeCalendar, gml:TimeCalendarEra, gml:TimeClock, gml:TimeOrdinalReferenceSystem, and gml:TimeOrdinalEra.