The Bank class is the root object class. An important function of a root object is to provide access to collections of other objects from the model classes. In this tutorial, only the allCustomers collection is exposed to .NET.
When you run the exposure wizard, selecting a reference automatically selects the type of that reference; for example, selecting allCustomers automatically exposes the CustomersByLastName dictionary class; that is, you do not have to decide which collection classes to select in the exposure wizard.
The properties and methods related to sequence numbers are not exposed, even though they are used by the create method of the Customer class to generate a unique customer number.
