8.7 Exercises

1. Using the ourEng.pl grammar, give a detailed top-down depth-first analysis of Marsellus knew Vincent loved Mia. That is, start with:

   

   and then show all the steps of your work, including the backtracking.

2. Using the ourEng.pl grammar, give a detailed top-down breadth-first analysis of Marsellus knew Vincent loved Mia. That is, start with:

   

   and then show all the steps of your work.

3. Can topdown_recognizer.pl and topdown_parser.pl handle the following grammar?

   s ---> [left,right].
left ---> [left,x].
left ---> [x].
right ---> [right,y].
right ---> [y].
 
lex(a,x).
lex(b,y).

   If you are not sure try it. Why does it not work? How can it be fixed?

4. In terms of bottom us vs. top down and depth-first vs. breadth-first, what parsing strategy is used by Prolog's built in DCG mechanisms? If you are not sure, write a DCG corresponding to ourEng.pl and trace through an example comparing what happens to the different strategies that you have seen in the last two chapters.