-*- mode:Text -*-
Copyright 1992 Patrick H. Winston.  All rights reserved.
Version 1.1.1, transferred from master disk on 23 Apr 93
 
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PURPOSE

Provides program support for Chapter 7, Rules and Rule Chaining.
Illustrates forward chaining via grocery bagging.

WARNING

To produce more interesting behavior, the bag-changing thresholds
in the program are different from those in the book.  In
particular, a new bag is started after 3 large items, 6 medium
items, or 12 small items, not 6, 12, and 18.

PERFORMANCE EXPERIMENT 1

Examine the file bagger.exp.  Run the experiment by typing the
following command to your lisp system:

(load "bagger.exp")

Alternatively, evaluate each Lisp expression in the file one at a
time, noting what each does.

PERFORMANCE EXPERIMENT 2

Change the grocery list by editing the grocery list in the
bagger.lsp file.  Run Bagger again with your altered list.

KNOWLEDGE ENGINEERING EXPERIMENT 1

Improve the bagger program by editing the rules in the bagger.lsp
file so as to allow up to five small items to be placed in any
bag that already contains large or medium items.

KNOWLEDGE ENGINEERING EXPERIMENT 2

Rewrite the bagger rules so as to have Bagger bag groceries by
using the accumulated volume of the groceries bagged, rather than
by counting.

SMALL-SCALE LISP PROJECT

Add a feature to the forward-chaining apparatus so that you can
specify what cannot be true, as well as what must be true, among
the rules's antecedents.

MEDIUM-SCALE LISP PROJECT

As it stands, variables are denoted, awkwardly, by lists like
this: (? bag).  Write Lisp reader macros so that variables are
denoted by question mark prefixes like this: ?bag.

LARGE-SCALE LISP PROJECT

Incorporate the rete procedure into the forward chaining
procedure.