This class is used to load the evaluators required for evaluating fields.

This class acts as the interface between the field framework and applications that implement evaluators. An application that implements evaluators should derive from this class and register an object of this class with the field engine when the application is loaded. The registered loader is used by the engine to obtain the evaluator object. Only one loader object is required for an application and it can support multiple evaluators. The loader objects are maintained globally and are used by all open documents.