This class represents an answer or a response to a question on the Short-Form McGill Pain Questionnaire (SF-MPQ) Assessment Instrument. This abstract class exists primarily to re-define the generic AssessmentEvent.responseItem.answer property to the SF-MPQ.responseItem.answer. In other words, of all the possible answers on all the possible kinds of assessment instruments, we are explicitly identifying the possible answers to the ten SF-MPQ questions. Note that because this class is abstract, implementers would likely not instantiate this class, but rather the ten concrete sub classes.