Breaking the reference answer down into fine-grained facets permits a more focused assessment of the student's response, but a simple yes or no entailment at the facet level still lacks semantic expressiveness with regard to the relation between the student's answer and the facet in question, (e.g., did the student contradict the facet or completely fail to address it?)
it is also necessary to break the annotation labels into finer levels in order to specify more clearly the relationship between the student's answer and the reference answer facet.