and relationships with other objects. How an object updates itself as its context
changes is called its behavior. The system-provided object classes predefi
ne what is a wall, slab, or roof in terms of how they interact with other objects.
Companies should have the capability of developing user-defi ned
parametric objects—both new ones and extensions of existing ones—and corporate
object libraries for customized features and to establish their own best
practices. Object attributes are needed to interface with analyses, cost estimations,
and other applications, but these attributes must fi rst be defi ned by the
fi rm or user.