Feedback rules are used to interpret the answer and give appropriate feedback.
To understand the difference between positive and negative feedback, it's important to understand SOWISO's evaluation flow, displayed in the figure below.
Here's how it works
The user inserts a formula using the keyboard and optionally, also the virtual keyboard. When the answer contains a syntax error, this is immediately show on screen.
a. based on the selected evaluation type, sometimes feedback can be given for an incorrect form. For example. for some evaluation types it is always necessary to get the answer in the form of an equation. If this is not the case, default feedback will be given.b. the solution rules are checked for mathematical equivalence.
If a positive feedback rule is hit, the corresponding feedback is presented and the user is not ´finished´ with the exercise in a formative setting, or in a test he will only get a partial score based on the test usage field.
If a negative feedback rule is hit, the corresponding feedback is presented and the user is not ´finished´ with the exercise, or in a test he will he will only get a partial score (or 0) based on the test usage field.
Finally, if the answer is correct according to the solution(s) and no positive feedback rules are hit, the answer is marked correct, the student is ´finished´ with the exercise and can progress, or receives the full score in a test.
More technical information can be found here, under Evaluation flow and Feedback (Navigate using the white tab on the left).