SAIF provides a means of defining explicit relationships between two objects. A subclass of Relationship is SpatialRelationship, which acts as the parent class for a number of topologic and metric (involving measurements) associations. The two objects referenced in a spatial relationship must both be geographic objects. Spatial topology introduces concepts such as adjacent, contains, surrounds, boundedBy, on the left side of, and so on. The metric associations include relationships such as spatial neighbourhood, distance from, distance and angles, and relative linear distance.
Although the two objects in a spatial or temporal relationship (see below) are geographic objects, any calculations required to establish such a relationship will involve the spatial or spatiotemporal objects associated with the geographic objects. For example someone might ask whether one street intersects another street. The mechanism for answering the query, hidden from the user, will involve comparisons of their respective geometries.
2.4.11 TemporalRelationship
TemporalRelationship is a subclass of Relationship. As such, temporal relationships are always implemented as relationships between two geographic objects. The geographic objects referenced in the temporal relationship should have positions specified from the class SpatiotemporalObject. Several subclasses of TemporalRelationship are specified in SAIF, including TemporalTopology, Precedence, TemporalProximity, TemporalNeighbourhood, and TemporalOffset. Users may add their own subclasses of TemporalRelationship.