flex Expert System Toolkit - LPIS

11. Example – Robbie Goes Shopping 162
rule pack_frozen_item
if the shopping includes an Item
and the Item`s condition is frozen
then pack_item( Item ) .
rule pack_large_bottle
if the shopping includes an Item
and the Item`s container is a bottle
and the Item`s size is large
then pack_item( Item ) .
rule pack_other_large_item
if the shopping includes an Item
and the Item`s size is large
then pack_item( Item ) .
rule pack_medium_item
if the shopping includes an Item
and the Item`s size is medium
then pack_item( Item ) .
rule pack_small_item
if the shopping includes an Item
and the Item`s size is small
then pack_item( Item ) .
The initial rule agenda should be structured to reflect the order in which the
rules are meant to be fired (i.e. check for frozen items first, then large bottles
etc.).
We note that if the conditions of a rule are not satisfied, they will not
become satisfied at any later stage. In this case the most efficient way to
update the rule agenda is to remove any unsatisfied rules.
The ruleset which governs this use of the forward chaining rules is defined in
the following way. The order and contents of the initial rule agenda is
determined in the ruleset, by the part indicated by the KSL keyword
contains.
ruleset packing_rules
contains
pack_frozen_item,
pack_large_bottle,
pack_other_large_item,
pack_medium_item,
pack_small_item ;
select rule using first come first served ;
update ruleset by removing any unsatisfied rules .
Packing The Items
flex toolkit
We do not know in advance how many carrier bags will be needed when
packing the groceries. So, each carrier bag must be generated as and when