1. An article of digital data storage media encoded with instruction code that is operable on a data processing system for determining during program execution the class of an object to instantiate, the instruction code comprising: instruction code configured for ascertaining a set of input data items, the set defining a number of input data items; instruction code configured for looping through members of a set of two or more candidate object classes, each member of the set defining a number of candidate data items; instruction code configured for comparing the number of input data items with the number of candidate data items of each member of the set of candidate object classes, thereby determining whether each candidate object class is or is not a potentially successful candidate object class, those candidate object classes having a number of candidate data items equal to or greater than the number of input data items determined to be potentially successful candidate object classes; instruction code configured for identifying a successful candidate object class from the set based at least in part on the determination whether each candidate object class is or is not a potentially successful candidate object class; and instruction code configured for instantiating the object based at least in part on the identified successful candidate object class.