10. The computer-implemented method of claim 1 , wherein the metric score is a score within a scale from zero to one, and wherein generating the metric score further comprises: calculating an amount of word sequence overlap between the machine-generated response and a reference response in the set of multi-reference responses, wherein an overlap of zero indicates no words in common between the machine-generated response and the reference response, and wherein an overlap of one indicates the machine-generated response is identical to the reference response.
10. The computer-implemented method of claim 1 , wherein the metric score is a score within a scale from zero to one, and wherein generating the metric score further comprises: calculating an amount of word sequence overlap between the machine-generated response and a reference response in the set of multi-reference responses, wherein an overlap of zero indicates no words in common between the machine-generated response and the reference response, and wherein an overlap of one indicates the machine-generated response is identical to the reference response. 11. The computer-implemented method of claim 10 , further comprising: on determining an overlap between the machine-generated response and the references response, determining a rating of the reference response; increasing the metric score on determining the rating of the reference response is a positive rating; and decreasing the metric score on determining the rating of the reference response is a negative rating.