Let’s say we have an exercise where the answer is x+3*x*y+3*y. Without positive feedback rules, an answer like 3*x+4*y+z+3*x*y−2*x−z-y would also be considered fully correct. However, we want the student answer to

Contain no other variables than x and y

Contain variables x and y both exactly twice

Contain no other symbols than times and plus

Contain the symbol plus exactly twice and contain the symbol times exactly three times

These requirements on the student’s answer can be implemented using positive feedback rules.

An explanation of what positive feedback rules are can be found here. More information on how to add positive feedback rules can be found here. Lastly, more information on evaluation types can be found here.

Below, we see an example of what the positive feedback of this exercise could look like, considering the requirements given above.