Dynamic properties DynamicFeature DynamicFeatureCollection

170 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. The content model extends gml:DynamicFeatureType with the gml:dynamicMembers property: complexType name=DynamicFeatureCollectionType complexContent extension base=gml:DynamicFeatureType sequence element ref=gml:dynamicMembers sequence extension complexContent complexType element name=dynamicMembers type=gml:DynamicFeatureMemberType complexType name=DynamicFeatureMemberType complexContent extension base=gml:AbstractFeatureMemberType sequence element ref=gml:DynamicFeature minOccurs=0 maxOccurs=unbounded sequence attributeGroup ref=gml:AssociationAttributeGroup extension complexContent complexType A gml:DynamicFeatureCollection is a feature collection that has a gml:validTime property i.e. is a snapshot of the feature collection or which has a gml:history property that contains one or more gml:AbstractTimeSlices each of which contain values of the time varying properties of the feature collection. Note that the gml:DynamicFeatureCollection may be one of the following: 1. A feature collection which consists of static feature members members do not change in time but which has properties of the collection object as a whole that do change in time 6 . EXAMPLE 1 A Train: The Train is a feature collection. The position and speed of the train are time varying and could be captured in the history of the Train. The featureMembers of the Train are the individual cars including the locomotive. The properties of the cars are static such as the position of the car in the train we ignore any re-organization of the train in this example, the cargo, the make of the car and its type e.g. grain car, oil car etc.. 2. A feature collection which consists of dynamic feature members the members are gml:DynamicFeatures but which also has properties of the collection as a whole that vary in time. EXAMPLE 2 A collection of sail boats in a yachting race. The sail boats may disappear from the race or reappear. The area encompassing the boats in the race think of a race like the Vendée Globe would be time variant. NOTE One may also have a feature collection with dynamic feature members but such that the properties of the collection as a whole are static. This might also be applied to the sail boat race where we only have properties like the organization committee, and the location of the starting point and finish line.

14.5.6 AbstractTimeSlice

To describe an event — an action that occurs at an instant or over an interval of time — GML provides the gml:AbstractTimeSlice element, which is declared as follows: element name=AbstractTimeSlice type=gml:AbstractTimeSliceType abstract=true 6 e.g. described by a history. Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 171 substitutionGroup=gml:AbstractGML complexType name=AbstractTimeSliceType abstract=true complexContent