PDDL Graphplan can't find plan

问题:

I've written a domain and a test problem in PDDL, but apparently the graphplan implementation can't find a plan. Here's the domain:

(define (domain aperture)     (:requirements :strips :typing :negative-preconditions)     (:types         cube         hallway room - location         )     (:predicates         (at ?l - location)         (has ?c - cube)         (connected ?l1 - location ?l2 - location)         (in ?c - cube ?l - location)         )     (:action enter         :parameters (?h - hallway ?r - room)         :precondition (and (connected ?h ?r) (connected ?r ?h) (at ?h)                         (not (at ?r)))         :effect (and (at ?r) (not (at ?h)))         )     (:action exit         :parameters (?r - room ?h - hallway)         :precondition (and (connected ?r ?h) (connected ?h ?r) (at ?r)                         (not (at ?h)))         :effect (and (at ?h) (not (at ?r)))         )     (:action move         :parameters (?h1 ?h2 - hallway)         :precondition (and (connected ?h1 ?h2) (connected ?h2 ?h1)                             (at ?h1) (not (at ?h2)))         :effect (and (at ?h2) (not (at ?h1)))         )     (:action pickup         :parameters (?c - cube ?l - location)         :precondition (and (at ?l) (not (has ?c)) (in ?c ?l))         :effect (and (has ?c) (not (in ?c ?l)))         )     (:action drop         :parameters (?c - cube ?l - location)         :precondition (and (at ?l) (has ?c) (not (in ?c ?l)))         :effect (and (not (has ?c)) (in ?c ?l))         ) ) 

and here's the problem:

(define (problem pb1)   (:domain aperture)   (:requirements :strips :typing)    (:objects h1 - hallway         h2 - hallway         h3 - hallway         r1 - room         c1 - cube)   (:init (at h1)      (connected h1 h2)      (connected h2 h1)      (connected h2 h3)      (connected h3 h2)      (connected h2 r1)      (connected r1 h2)      (in c1 r1)      )   (:goal (and        (has c1)       )     ) ) 

For this particular problem the set of states for the solution should be:

move(h1,h2) enter(h2,r1) pickup(c1,r1) 

but, as I've said, the graphplan implementation that I'm using (graphplan) can't find any plan.

回答1:

I was able to find a solution plan using strips. However, I had to tweak your domain slightly. Specifically, I changed the domain actions "pickup" and "drop" to replace the parameter type "location" with "room". With this change, I was able to find the following solution:

1. move h1 h2 2. enter h2 r1 3. pickup c1 r1 

Maybe this could be the reason graphplan was unable to find a solution as well? Here are the modified domain and problem pddl files.

domain.pddl

(define (domain aperture)     (:requirements :strips :typing :negative-preconditions)     (:types         cube         hallway room - location         )     (:action enter         :parameters (?h - hallway ?r - room)         :precondition (and (connected ?h ?r) (connected ?r ?h) (at ?h)                         (not (at ?r)))         :effect (and (at ?r) (not (at ?h)))         )     (:action exit         :parameters (?r - room ?h - hallway)         :precondition (and (connected ?r ?h) (connected ?h ?r) (at ?r)                         (not (at ?h)))         :effect (and (at ?h) (not (at ?r)))         )     (:action move         :parameters (?h1  - hallway ?h2 - hallway)         :precondition (and (connected ?h1 ?h2) (connected ?h2 ?h1)                             (at ?h1) (not (at ?h2)))         :effect (and (at ?h2) (not (at ?h1)))         )     (:action pickup         :parameters (?c - cube ?l - room)         :precondition (and (at ?l) (not (has ?c)) (in ?c ?l))         :effect (and (has ?c) (not (in ?c ?l)))         )     (:action drop         :parameters (?c - cube ?l - room)         :precondition (and (at ?l) (has ?c) (not (in ?c ?l)))         :effect (and (not (has ?c)) (in ?c ?l))         ) ) 

problem.pddl

(define (problem pb1)   (:domain aperture)   (:objects h1 - hallway         h2 - hallway         h3 - hallway         r1 - room         c1 - cube)   (:init (at h1)      (connected h1 h2)      (connected h2 h1)      (connected h2 h3)      (connected h3 h2)      (connected h2 r1)      (connected r1 h2)      (in c1 r1)      )   (:goal (and        (has c1)       )     ) ) 

文章来源: PDDL Graphplan can't find plan