Initiates processing of a collection. This method starts the processing in another thread and returns immediately. Status of the processing can be obtained by registering a listener with the {@link #addStatusCallbackListener(StatusCallbackListener)} method.
A CPE can only process one collection at a time. If this method is called while a previous processing request has not yet completed, a UIMA_IllegalStateException
will result. To find out whether a CPE is free to begin another processing request, call the {@link #isProcessing()} method.
@throws ResourceInitializationException if an error occurs during initialization
@throws org.apache.uima.UIMA_IllegalStateException if this CPE is currently processing