flex Expert System Toolkit - LPIS

Appendix A - Examples 178
group start_rules
fill_master, fill_slave .
The Ruleset
The problem starts with both jugs being empty, we can therefore limit the
initial rule agenda to two rules: the rule that fills the master jug and the rule
that fills the slave jug. For convenience we have put these rules in a group
called start_rules. The rule agenda will subsequently be updated using
the rule transition network that we defined above.
We have attached scores to the rules to give them different chances of being
selected according to the situation. The rules will then be selected using the
conflict resolution scoring system with a threshold of 6. This means that the
first rule found whose score is above 6 will be fired.
The solution to the problem will be found (so we want the forward chaining
engine to terminate) if at any point the contents of any container are 6.
The ruleset that defines this method of selecting rules, updating the rule
agenda and terminating the forward chaining is written as follows.
ruleset water_jugs
contains start_rules ;
select rule using
conflict resolution with threshold 6 ;
update ruleset using rule transition network ;
initiate by doing restart ;
terminate when
the contents of any container are 6 .
The action that triggers the whole program can then be written as follows. (The
spy_chain/0 built-in flex predicate causes execution information to be written to the
current output stream.)
action demo ;
do spy_chain
and invoke ruleset water_jugs .
flex toolkit