6.0 Object Functionality

This section of the standard discusses the requirements for improving the functionality and performance of BIM objects so as not to detrimentally affect the performance of a model into which they may be placed.

6.4 Parametric behaviour

  6.4 Parametric behaviour
This sub-section of the standard discusses the requirements for creating objects with parametric behaviour.
 6.4.1 Functional behaviour
  Parametric objects that are reliant upon host objects in/on which they are placed, shall be created with the specific functionality to manipulate the host object, or vice versa, as necessary to suit their purpose. Such as a parametric window object that shall be modelled so as to create a corresponding void in the wall object into which it would be placed or alternatively if the wall thickness changed the window dimension would adjust to suit.
 6.4.2 Geometric behaviour
  Parametric objects shall be created when an object can represent geometrical variants of an object type.
The parametric capability of the object shall be limited to the available variants of the physical element it represents. For example, if a physical element is available in 4 different lengths, limit the parametric length function of the object to those 4 available lengths.
 6.4.3 Multiple IFC types

Objects shall not be created with parametric capability to allow the object to represent multipleIfcElementType’s. For example, do not create one object that can represent a bath and also represent a sink, as these objects are represented by different IfcElementType's.
In this situation duplicate parametric objects shall be created and assigned the corresponding IfcElementType, one to represent each IfcElementType required. For example, one to represent a parametric bath and one to represent a parametric sink.

 6.4.4 Reference items
  When modelling objects with parametric geometry, the parametric behaviour shall be controlled by reference items such as planes, lines or points.
 6.4.5 Use limitation
  The use of parametric behaviour shall be limited to that deemed necessary, or required, to avoid over-constraining the functionality of the object.