Class

• <DRM Edge Direction>

Superclass

• <DRM SEDRIS Abstract Base>

Subclass

• None.

Definition

An instance of this DRM class specifies, for the associated relationship, whether the target edge should be traversed forwards (from start node to end node) or backwards (in the opposite direction).

If the value of the forwards field is TRUE, the edge is oriented in the same direction as the object with which it is associated, so that it should be traversed from its starting node to its ending node.

If the value of the forwards field is FALSE, either the orientation of the edge is the opposite of that of the associated object, or the associated object has no clearly defined orientation. In this case, the edge should be traversed from ending node to starting node.

Class diagram

Figure 6.74 — DRM_Edge_Direction

Constraints

• Publishable object

Example(s)

• A <DRM Linear Feature> instance representing a stream is associated with several <DRM Feature Edge> instances that define the path of the stream. The <DRM Edge Direction> link object associated with each <DRM Feature Edge> instance has forwards = TRUE if the <DRM Feature Edge> instance is oriented so that the stream flows in the direction from its starting node to its ending node, and FALSE if the stream flows in the opposite direction.

• Consider a <DRM Linear Feature> instance representing a one-way street. Its path is defined by a <DRM Feature Edge> instance, so that the <DRM Edge Direction> link object between the <DRM Linear Feature> instance and the <DRM Feature Edge> instance indicates whether the orientation of the <DRM Feature Edge> instance matches the permitted direction of travel along the one-way street.

• The external <DRM Feature Face Ring> instance of a regular <DRM Feature Face> instance consists of three <DRM Feature Edge> instances. In traversing the ring, the first <DRM Feature Edge> instance might be traversed from starting node to ending node, so that its <DRM Edge Direction> link object has forwards = TRUE If the next <DRM Feature Edge> instance was traversed from its ending node (which in this example is the same <DRM Feature Node> instance as the ending node of the previous <DRM Feature Edge> instance) to its starting node, its <DRM Edge Direction> link object has forwards = FALSE (that is, backward).