Advanced Customization > Services and Infrastructure Customization > The Enterprise Layer > Enterprise Abstractions
  
Enterprise Abstractions
The wt.enterprise package provides the basic business objects used in the Windchill system. Most business classes you construct will be extended from the enterprise classes or their subclasses.
The enterprise Package
Business classes should be extended from one of the abstract classes included in the wt.enterprise package to take advantage of the capabilities and services they offer. This diagram shows convenience classes designed to consolidate a basic set of features that various business classes might require. Most of the business classes in your model are expected to extend one of these classes and simplify your implementations.