4.1.4.4.1.2 Alignment Layout - Reusing Horizontal Layout

Nesting and aggregation relationships between IfcAlignment's and their layouts, in the case where multiple alignments re-use the same horizontal layout definition.

In the diagram below is an example of a parent alignment, with the horizontal layout, and two child alignments, one with a vertical layout, and the other with a vertical and a cant layout; both re-using the definition of the horizontal layout from the parent alignment.

When defining the list of segments for the business logic (i.e., IfcAlignmentHorizontalSegment, IfcAlignmentVerticalSegment, IfcAlignmentCantSegment):

1. A zero-length segment shall be added, at the end of the list of segments for IfcAlignmentSegment.DesignParameters.
2. If the geometry definition is also present, then each of the zero-length segments shall have a IfcCurveSegment counterpart - of length zero.

The following diagram shows the generic classes and relationships used when applying this concept. In addition, concepts may have particular importance to common or standardised industry practices and scenarios. For these specific usage scenarios, the table below shows a recommended list of general usage patterns that users may adopt.

General Usage

ApplicableEntity
IfcAlignment