3 Mar 2004
CS3243 - Inference
26
Efficiency of forward chaining
Incremental forward chaining: no need to match a rule on
iteration k if a premise
wasn't added on iteration k-1
Þ match each rule
whose premise contains a newly added positive literal
Matching itself can be expensive:
Database indexing allows O(1) retrieval of known facts
¡e.g., query Missile(x)
retrieves Missile(M1)
Forward chaining is widely used in deductive databases