How should Prolog computation Be represented for practical use?

We propose a visual computation model called theBox and Plane Model (BPM), which visually clarifies the semantics of backtracking, the cut operator, and side-effects, thus allowing the procedural features of Prolog to be grasped. On the bases of the BPM, we developed a visual debugger for Prolog, PROEDIT2, which has proved that this kind of pragmatic computation model for Prolog increases the efficiency of the debugging work.