%-----------------------------------------------------------------------------
% DESS version of the rule-based reaction system "BAGGER", which is described
% in:
%	"Artificial Intelligence" (3rd Edition)
%	Patrick Henry Winston
%	Addison Wesley (1992), pp 129-137.
%-----------------------------------------------------------------------------

bag subclass of container with
	contents: [cardinality: multi]
	number_of_large_items: 0
	number_of_medium_items: 0
	number_of_small_items: 0;

bag1 instance of bag;			% Empty bags (instances).
bag2 instance of bag;
bag3 instance of bag;
bag4 instance of bag;

the is_frozen of item is no;		% Items are not frozen.
the in_freezer_bag of item is no;	% Items are not in freezer bags.

bread instance of item with		% Items (instances)
	container_type: plastic_bag
	size: medium;

glop instance of item with		% Don't know what this is!
	container_type: jar
	size: small;

granola instance of item with		% Don't know what this is!
	container_type: cardboard_box
	size: large;

ice_cream instance of item with
	container_type: cardboard_carton
	size: medium
	is_frozen: yes;			% Ice cream is frozen

potato_chips instance of item with
	container_type: plastic_bag
	size: medium;

pepsi instance of item with
	container_type: bottle
	size: large;

add frame bag1;			% Load bag frames into working memory.
add frame bag2;
add frame bag3;
add frame bag4;

add frame bread;		% Load item frames into working memory.
add frame glop;
add frame granola;
add frame ice_cream;
add frame potato_chips;
add frame pepsi;

the current_bag of order is bag1;

the items_to_be_bagged of order include bread;
the items_to_be_bagged of order include glop;
the items_to_be_bagged of order include granola;
the items_to_be_bagged of order include ice_cream;
the items_to_be_bagged of order include potato_chips;


'step is check-order';					% Initial context.


rule B1
	if	'step is check-order' and
		the items_to_be_bagged of order include potato_chips and
		not(the items_to_be_bagged of order include pepsi) and
		ask 'Do you want Pepsi added to the order (y/n)? ' = y
	then	the items_to_be_bagged of order include pepsi;

rule B2
	if	'step is check-order'
	delete	'step is check-order'
	add	'step is bag-large-items';

rule B3
	if	'step is bag-large-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is large and
		the container_type of Item is bottle and
		the current_bag of order is Bag and
		the number_of_large_items of Bag is L and
		L < 6
	delete	the items_to_be_bagged of order include Item and
		the number_of_large_items of Bag is L
	add	the contents of Bag include Item and
		the number_of_large_items of Bag is L + 1;

rule B4
	if	'step is bag-large-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is large and
		the current_bag of order is Bag and
		the number_of_large_items of Bag is L and
		L < 6
	delete	the items_to_be_bagged of order include Item and
		the number_of_large_items of Bag is L
	add	the contents of Bag include Item and
		the number_of_large_items of Bag is L + 1;

rule B5
	if	'step is bag-large-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is large and
		NewBag is an instance of bag and
		the number_of_large_items of NewBag is 0 and
		the number_of_medium_items of NewBag is 0 and
		the number_of_small_items of NewBag is 0 and
		the current_bag of order is Bag
	delete	the current_bag of order is Bag
	add	the current_bag of order is NewBag;

rule B6
	if	'step is bag-large-items'
	delete	'step is bag-large-items'
	add	'step is bag-medium-items';

rule B7
	if	'step is bag-medium-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is medium and
		the is_frozen of Item is yes and
		the in_freezer_bag of Item is no
	delete	the in_freezer_bag of Item is no
	add	the in_freezer_bag of Item is yes;

rule B8
	if	'step is bag-medium-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is medium and
		the current_bag of order is Bag and
		the number_of_large_items of Bag is 0 and
		the number_of_small_items of Bag is 0 and
		the number_of_medium_items of Bag is M and
		M < 12
	delete	the items_to_be_bagged of order include Item and
		the number_of_medium_items of Bag is M
	add	the contents of Bag include Item and
		the number_of_medium_items of Bag is M + 1;

rule B9
	if	'step is bag-medium-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is medium and
		NewBag is an instance of bag and
		the number_of_large_items of NewBag is 0 and
		the number_of_medium_items of NewBag is 0 and
		the number_of_small_items of NewBag is 0 and
		the current_bag of order is Bag
	delete	the current_bag of order is Bag
	add	the current_bag of order is NewBag;

rule B10
	if	'step is bag-medium-items'
	delete	'step is bag-medium-items'
	add	'step is bag-small-items';

rule B11
	if	'step is bag-small-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is small and
		the current_bag of order is Bag and
		the number_of_large_items of Bag is 0 and
		the number_of_medium_items of Bag is 0 and
		the number_of_small_items of Bag is S and
		S < 18
	delete	the items_to_be_bagged of order include Item and
		the number_of_small_items of Bag is S
	add	the contents of Bag include Item and
		the number_of_small_items of Bag is S + 1;

rule B12
	if	'step is bag-small-items' and
		the items_to_be_bagged of order include Item and
		the size of Item is small and
		NewBag is an instance of bag and
		the number_of_large_items of NewBag is 0 and
		the number_of_medium_items of NewBag is 0 and
		the number_of_small_items of NewBag is 0 and
		the current_bag of order is Bag
	delete	the current_bag of order is Bag
	add	the current_bag of order is NewBag;

rule B13
	if	'step is bag-small-items'
	delete	'step is bag-small-items'
	add	'step is done';