TimeOrdinalReferenceSystem, TimeOrdinalEra Ordinal temporal reference systems .1 Overview

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 167 gml:member properties which indicate ordered gml:TimeOrdinalEra elements, and a gml:group property which points to the parent era. This is declared as follows: element name=TimeOrdinalEra type=gml:TimeOrdinalEraType complexType name=TimeOrdinalEraType complexContent extension base=gml:DefinitionType sequence element name=relatedTime type=gml:RelatedTimeType minOccurs=0 maxOccurs=unbounded element name=start minOccurs=0 type=gml:TimeNodePropertyType element name=end minOccurs=0 type=gml:TimeNodePropertyType element name=extent type=gml:TimePeriodPropertyType minOccurs=0 element name=member type=gml:TimeOrdinalEraPropertyType minOccurs=0 maxOccurs=unbounded element name=group type=gml:ReferenceType minOccurs=0 sequence extension complexContent complexType The recursive inclusion of gml:TimeOrdinalEra elements allow the construction of an arbitrary depth hierarchical ordinal reference schema, such that an ordinal era at a given level of the hierarchy includes a sequence of shorter, coterminous ordinal eras. EXAMPLE The example below shows a portion of the geological time scale depicted as an ordinal reference system: gml:TimeOrdinalReferenceSystem gml:id=GeologicalTimeScale gml:description xlink:href=ftp:ftp.iugs.orgpubiugsiugs_intstratchart.pdf gml:nameGeological time scalegml:name gml:domainOfValidityEarthgml:domainOfValidity -- Earlier eras omitted -- gml:component gml:TimeOrdinalEra gml:id=Cenozoic gml:nameCenozoic Eragml:name gml:start xlink:href=basePaleocene gml:end xlink:href=now gml:member gml:TimeOrdinalEra gml:id=Tertiary gml:nameTertiary Periodgml:name gml:start xlink:href=baseTertiary gml:end xlink:href=basePleistocene gml:member gml:TimeOrdinalEra gml:id=Paleogene gml:namePaleogene sub-periodgml:name gml:start gml:TimeInstant gml:id=basePaleogene gml:timePosition frame=geologyMa65.0gml:timePosition gml:TimeInstant gml:start gml:end xlink:href=baseNeogene gml:member gml:TimeOrdinalEra gml:id=Paleocene gml:namePaleocene Epochgml:name gml:start xlink:href=basePaleogene gml:end xlink:href=baseEocene gml:TimeOrdinalEra gml:member gml:member gml:TimeOrdinalEra gml:id=Eocene gml:namePaleocene Epochgml:name gml:start 168 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. gml:TimeInstant gml:id=baseEocene gml:timePosition frame=geologyMa57.8gml:timePosition gml:TimeInstant gml:start gml:end xlink:href=baseOligocene gml:TimeOrdinalEra gml:member gml:member gml:TimeOrdinalEra gml:id=Oligocene gml:nameOligocene Epochgml:name gml:start gml:TimeInstant gml:id=baseOligocene gml:timePosition frame=geologyMa33.7gml:timePosition gml:TimeInstant gml:start gml:end xlink:href=baseNeogene gml:TimeOrdinalEra gml:member gml:TimeOrdinalEra gml:member -- Neogene sub-period and Quaternerary period omitted -- gml:TimeOrdinalEra gml:member gml:TimeOrdinalEra gml:component gml:TimeOrdinalReferenceSystem Note that the use of references on various begin and end elements allows the position of the boundaries between eras to be recorded once and then re-used many times as appropriate, corresponding to a non-linear graph when appropriate. All positions refer to a frame ―geologyMa‖ which would be defined as a temporal coordinate system e.g see Clause 12.

14.4.5.3 TimeOrdinalEraPropertyType

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

14.5 Representing dynamic features

14.5.1 Overview

A number of types and relationships are defined to represent the time-varying properties of geographic features. In a comprehensive treatment of spatiotemporal modelling, Langran see Bibliography distinguished three principal temporal entities: states, events, and evidence; the schema specified in the following subclauses incorporates elements for each. The conceptual model is shown in D.3.11.

14.5.2 dataSource

In GML, evidence is represented by a simple gml:dataSource or gml:dataSourceReference property that indicates the source of the temporal data. Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 169 element name=dataSource type=gml:StringOrRefType element name=dataSourceReference type=gml:ReferenceType The remote link attributes of the gml:dataSource element have been deprecated along with its current type. To refer to a remote data source, use the remote link attributes of gml:dataSourceReference instead. EXAMPLE A human observer or an in situ sensor.

14.5.3 Dynamic properties

A convenience group gml:dynamicProperties is defined as follows: group name=dynamicProperties sequence element ref=gml:validTime minOccurs=0 element ref=gml:history minOccurs=0 element ref=gml:dataSource minOccurs=0 element ref=gml:dataSourceReference minOccurs=0 sequence group This allows an application schema developer to include dynamic properties in a content model in a standard fashion. The gml:validTime property is specified in 14.2.1.3. The other properties are specified elsewhere in 14.5.

14.5.4 DynamicFeature

States are captured by time-stamped instances of a feature. gml:DynamicFeature implements DynamicFeature as shown in D.3.11 and is declared as follows: element name=DynamicFeature type=gml:DynamicFeatureType substitutionGroup=gml:AbstractFeature The content model extends the standard gml:AbstractFeatureType with the gml:dynamicProperties model group: complexType name=DynamicFeatureType complexContent extension base=gml:AbstractFeatureType group ref=gml:dynamicProperties extension complexContent complexType Each time- stamped instance represents a ‗snapshot‘ of a feature. The dynamic feature classes will normally be extended to suit particular applications. A dynamic feature bears either a time stamp or a history. NOTE A history consists of a set of gml:AbstractTimeSlices and such time slices may contain any time varying properties. We might for example use such a mechanism to describe a feature with one property that varies in time.

14.5.5 DynamicFeatureCollection

gml:DynamicFeatureCollection implements DynamicFeatureCollection as shown in D.3.11 and is declared as follows: element name=DynamicFeatureCollection type=gml:DynamicFeatureCollectionType substitutionGroup=gml:DynamicFeature