“…However, researchers have reported 100 -1,000 hours of authoring time for one hour of instructions in ITSs [3]; in addition, ITSs usually require an underlying domain theory such that their applicability is limited in areas where problems and their solution strategies are not easy to formalize [4,5]. In such domains, data-driven approaches are possible, providing feedback based on a set of existing examples for (correct) solutions of the underlying task [5,6]: If the students requires a hint on how to change her attempt to get closer to a correct solution, it can be compared to a similar example from the set, and the dissimilarities between her attempt and the example can be contrasted or highlighted in order to help the student to improve her own solution [7,8,9].…”