diff -ur perl/AI/ExpertSystem/Simple/Knowledge.pm udrpwiz/AI/ExpertSystem/Simple/Knowledge.pm
--- perl/AI/ExpertSystem/Simple/Knowledge.pm	2004-04-28 12:35:02.000000000 -0400
+++ udrpwiz/AI/ExpertSystem/Simple/Knowledge.pm	2004-05-10 02:25:23.000000000 -0400
@@ -44,6 +44,10 @@
 
 	$self->{_value} = $value;
 	$self->{_setter} = $setter;
+	foreach (@{$self->{_setters}}) {
+		#print "Setting ", $_->{_name}, " to invalid<br>\n" if $_->{_state} ne "invalid";
+		$_->{_state} = "invalid" ;
+	}
 }
 
 sub get_value {
diff -ur perl/AI/ExpertSystem/Simple.pm udrpwiz/AI/ExpertSystem/Simple.pm
--- perl/AI/ExpertSystem/Simple.pm	2004-04-28 12:30:01.000000000 -0400
+++ udrpwiz/AI/ExpertSystem/Simple.pm	2004-05-10 02:25:23.000000000 -0400
@@ -153,6 +153,9 @@
 			$self->{_number_of_attributes}++;
 			$self->{_knowledge}->{$attribute} = AI::ExpertSystem::Simple::Knowledge->new($attribute);
 		}
+
+		$self->{_knowledge}->{$attribute}->{_setters} ||= [];
+		push @{$self->{_knowledge}->{$attribute}->{_setters}}, $self->{_rules}->{$name};
 	}
 
 	eval { $t->purge(); }