CS240A: Databases and Knowledge Bases
From Deductive Rules to Active Rules
Carlo Zaniolo
Department of Computer Science
University of California, Los Angeles
WINTER 2002
From Deductive Rules to Production Rules



Production rules to materialize recursive views:
closure(X,Y) : base(X,Y)
closure(X,Y) : closure(X,Z), base(Z,Y)
Initialization:
insert into transclosure
(select * from base)
Production rule:
create rule transclosure on base
when inserted
then insert into closure
(select inserted.fr, closure.to
from inserted, closure
where inserted.to = closure.fr)
Maintenance

Every time the database is changed recompute
the concrete view, or

Perform delta maintenance using techniques
similar to the differential fixpoint of deductive
databases
 Things
are more complex here because you can have
both additions ( + ) an subtractions ( - )
Example of Recursive View

Database:
Station(city, state).
Train(city1, city2).

Deductive rules:
r1. Route(c1,c2) : Train(c1,c2).
r2. Route(c1,c2) :
Route(c1,c3), Route(c3,c2).
r3. ReachCal(c) :
Station(c,s), s = ''California'‘.
r4. ReachCal(c) :
Route(c,c2), ReachCal(c2).
Insert Rules:
r1i.
+Route(c1,c2) :-
+ Train(c1,c2).
r2i1.
+Route(c1,c2) :-
+ Route(c1,c3), Route(c3,c1).
r2i2.
+Route(c1,c2) :-
Route(c1,c3), +Route(c3,c2).
r3i.
+ReachCal(c) :-
+Station(c,s), s = ''California''
r4i1.
+ReachCal(c) :-
+ Route(c,c1), ReachCal(c1).
r4i2.
+ReachCal(c) :-
Route(c,c1), +ReachCal(c1).
Delete Rules
Eliminate all suspect arcs
r1d.
- Route(c1,c2) :-
-Train(c1,c2)
r2d1. - Route(c1,c2) :-
-Route(c1,c3),
OLD_Route(c3,c2)
r2d2. - Route(c1,c2) :-
OLD_Route(c1,c3),
- Route(c3,c2)
r3d.
- ReachCal(c) :-
- Station(c,s),
s = ''California''
r4d1. - ReachCal(c) :-
- Route(c,c1),
OLD_ReachCal(c1)
r4d2. - ReachCal(c) :-
OLD_Route(c,c1),
- ReachCal(c1)
Reinsert rules
r1r.
+ Route(c1,c2) : -Route(c1,c2),
Train(c1,c2)
r2r.
+ Route(c1,c2) : -Route(c1,c2),
Route(c1,c3), Route(c3,c2).
r3r.
+ ReachCal(c) : -ReachCal(c),
Station(c,s), s = ''California''
r4r.
+ ReachCal(c) : - ReachCal(c),
Route(c,c1),ReachCal(c1).