flex Expert System Toolkit - LPIS

9. Flex Predicates 154
spied_chain
?- some_instance( whale, E ).
E = moby_dick
Test whether or not the forward chaining engine has a spypoint set on it.
spied_fact( ?Name )
Test whether or not a spypoint is currently set.
Example
?- spied_fact( X ).
X = dislikes
spied_rule( ?Name )
Test whether or not the named rule currently has a spypoint set on it.
Example
?- spied_rule( prescribe_lomotil ).
no
spied_slot(?Attribute, ?Frame )
Check whether or not a there is a spypoint on the Attribute and Frame.
A call to spied_slot/2 will backtrack through all currently spied slots and
unify Attribute with the name of the attribute and Frame with its frame.
The call fails if there are no current spypoints set.
Example
?- spied_slot( A, F) .
A = habitat, F = moby_dick
etc.
spy_chain
Set a spypoint on the forward chaining engine. Whenever there is a call to
forward_chain/[5,6,7] certain information will be written to the
current output stream. This information relates to the termination criterion
and the selection phase.
Furthermore, if any spypoints have been set on individual rules and those
rules are at some stage considered for selection, the conditions of those rules
will be traced by the debugger.
flex toolkit