14. The computer program product of claim 10 , wherein the plurality of validators are validators selected to be applied to the candidate answer based on the answer key data structure, and wherein the validation status object stores results of applying each of the plurality of validators to the candidate answer.
15. The computer program product of claim 14 , wherein the validation status object further stores, for at least one validator of the plurality of validators, a log of operations performed by the at least one validator and corresponding results of the operations performed by the at least one validator.