Constituent nodes can be used as constructions when creating nodes. The benefit of using these is that they are lighter weight. Constituent nodes are not top-level nodes. They can however be accessed by indexing into the Constituents of the top-level node. Constituent elements are passed the top-level node into their constructor.

transaction 1 modelChange 'Add baseCS, Change baseCS'
{
    node User.Objects.baseCS Bentley.GC.NodeTypes.CoordinateSystem
    {
        Technique                 = 'AtModelOrigin';
        GraphLocation             = <auto> {40.0, 40.0};
    }
    node User.Objects.baseCS Bentley.GC.NodeTypes.CoordinateSystem
    {
        Technique                 = 'AtModelOrigin';
        DGNModelName              = '3D Metric Design';
        GraphLocation             = {29.167, 81.667, 174.0, 0.0};
    }
}

transaction 2 script 'Create Line from constituent nodes'
{
    		Line ln = new Line("joiningLine");
    		Point startPoint = new Point(ln);
    		startPoint.ByCartesianCoordinates(baseCS, 1.2, 3.4, 0.0);
    		Point endPoint = new Point(ln);
    		endPoint.ByCartesianCoordinates(baseCS, 2.0, 4.5, 0.0);
    	    ln.ByPoints(startPoint, endPoint);
}

Here OpenBuildings™ GenerativeComponents automatically generates the name Constituents[0] for the StartPoint and Constituent[1] for the EndPoint.