It is the time when spring is dancing around the corner, and the ballet The Nutcracker has drawn a curtain on another season's stage. While reminiscing about the Sugar Plum Fairy's lissome steps gliding across the stage along with the light-hearted music notes, we might wonder how Pyotr Ilyich Tchaikovsky, together with choreographer Marius Petipa, first adapted and transformed the story into an artistic performance. These different forms of art-written words, musical notes, and bodily movements-are all served as sheer representations of one single story. The manifestations of art activities can be analogous to the theme of this special issue: Models of Representation in Computational Intelligence. In particular, representation plays an essential role in models, solutions, and data manipulated by CI and AI techniques as it affects model transparency and explainability, problem space, and search performance. On offering new directions in transforming problems for better manipulations and improving CI techniques, furthermore, the four Features articles in this issue provide novel designs and discoveries in this field.
