Building Definition Language

Reference Geometry provides nonphysical geometric constructs used to locate, align, constrain, measure, manufacture, assemble, inspect, or coordinate physical Entities.

Reference Geometry may include:

control points;

centerlines;

axes;

planes;

envelopes;

nominal surfaces;

alignment curves;

path lines;

survey points;

virtual intersections;

reference volumes.

Example:

reference_geometry Beam_B01_Axis {

type: line;

start: [0 mm, 0 mm, 0 mm];

end: [3600 mm, 0 mm, 0 mm];

coordinates: @Beam_B01.local_coordinates;

}

Reference Geometry shall not be interpreted as physical material unless explicitly associated with a physical Entity.

External reference geometry shall identify:

resource location;

format;

version;

coordinate system;

unit;

integrity value;

Reference Geometry may control several Entities, but its authority shall be defined. A construction control line may be authoritative for site placement, while a manufacturer datum controls internal Component geometry.

Deleted or superseded Reference Geometry shall remain traceable where installed Entities were placed from it.