['In', 'this', 'sense', ',', 'the', 'original', 'KPIs', 'constitute', 'the', 'N', '-', 'dimensional', 'vector', 'space', 'basis', ',', 'whereas', 'the', 'N^', 'synthetic', 'KPIs', 'represent', 'the', 'orthogonal', 'vectors', 'with', 'the', 'highest', 'variance', '.']