CPSC 322 - Lecture 7

The Proof Procedure, Once More, With Feeling

I. The top-down procedure with variables and recursion

Today I used crude, but I hope effective, PowerPoint animations
to review how the top-down proof procedure works.  First we 
had just constants, no variables, in a review of what we 
talked about last time.  Then we added variables, which 
requires that the interpreter makes the appropriate subtitutions,
that is, it binds the appropriate constants to the appropriate 
variables as the chosen clause from the knowledge base is resolved 
with the answer clause.  Then we added recursion to the mix.  

There's a nice formal description of the substitution process on 
pages 52 and 53 of your textbook.  You can see how it works in action
but loading the PowerPoint slides for today's lecture into PowerPoint
(or some PowerPoint slide reader clone that can probably be downloaded 
from the web) and clicking the advance button as fast as you like.
If you can't read PowerPoint, then you could print out the .pdf file
of the slides, staple all the sheets together on one side, and then
thumb through the sheets of paper real fast like the flip books we
used to have as kids back in the 1960s, before the invention of television, 
movies, or even electricity.