Negation of a state in defining a new command

[sultanalnahian]

While defining a new command in the logic file, is it possible to mention that certain state cannot be satisfied? For example, I have a game scenario where, you can ask a information to a person. The question can be asked until the person gives the answer. When the person has given the information, you cannot ask the question again. So, I have defined a predicate "asked(pr)", which represents the state when the question has been asked already. And the rule is "ask/pr(pr)" which will be available only when the question was not asked before. So how can I add not "asked(pr)" state in the rule definition?

[MarcCote]

Hi @sultanalnahian, thanks for reaching out. The logic engine powering TextWorld uses the open-world assumption which means that not seeing a particular predicate in the state, does not mean it is false.

In your example, a workaround would be to define both asked(topic, person) and not_asked(topic, person) predicates. Then your ask rules could be something like

ask :: $at(P, r) & $at(person, r) & not_asked(topic, person) -> asked(topic, person);

NB: of course, you'll need to add all the relevant not_asked(...) predicates to the initial state.

[sultanalnahian]

Hi @sultanalnahian, thanks for reaching out. The logic engine powering TextWorld uses the open-world assumption which means that not seeing a particular predicate in the state, does not mean it is false.

In your example, a workaround would be to define both asked(topic, person) and not_asked(topic, person) predicates. Then your ask rules could be something like

ask :: $at(P, r) & $at(person, r) & not_asked(topic, person) -> asked(topic, person);

NB: of course, you'll need to add all the relevant not_asked(...) predicates to the initial state.

Hi @MarcCote, thanks for the reply. After executing the ask command, will the state not_asked be changed to the asked state? Does it mean that, the not_asked state is no longer true and as a result ask command cannot be executed again?

[MarcCote]

Yes. Your understanding is correct. If I'm not mistaking, that's what you were trying to do, right?

[sultanalnahian]

Yes, that's right. But It is not working. After giving the ask command, the command should not be shown in the game play as not_asked state is false now. But still the ask command is showing in the game play and it can be executed again. I am posting the person logic file below. Can you please, let me know what I have done wrong?

# person
type pr : t{
    predicates {
        attacked(pr);
        asked(pr);
	not_asked(pr);
    }
    rules {
        attack/pr   :: $at(P, r) & $at(pr, r) -> attacked(pr);
        ask/pr :: $at(P, r) & $at(pr,r) & $in(f, I) & $raw(f) & not_asked(pr) -> asked(pr);
    }
    constraints {
    # Predicate conflicts
    	pr1 :: asked(pr) & not_asked(pr) -> fail();
    }
    inform7 {   
        type {
            kind :: "person";
            definition :: "Person can be attacked. Person can be asked. Person is fixed in place.";
        }

        predicates {
            attacked(pr) :: "The {pr} is attacked";
            asked(pr) :: "The {pr} is asked";
            not_asked(pr) :: "The {pr} is not asked";
        }

        commands {
            attack/pr :: "attack {pr}" :: "_attacking {pr}";
            ask/pr :: "ask the {pr} about the bank robbery" :: "_ask the {pr} about the bank robbery";
        }
	code :: """
            Understand the command "attack" as something new.
            Understand "attack [something]" as _attacking.
            _attacking is an action applying to a thing.

            After _attacking a person:
		say "[the noun] is being attacked.";
            
            Understand the command "ask" as something new.
            Understand "ask [something]" as _asking.
            _asking is an action applying to a thing.

            After _asking a person:
		say "[the noun] has given the information. he said go north.";
           """;
    }
}

[MarcCote]

I think you need _asking instead of _ask in the last section of the Inform7 ask command.

commands {
        ....
            ask/pr :: "ask the {pr} about the bank robbery" :: "_ask the {pr} about the bank robbery";
        }

I just create a PR that will enable you to see what Inform7 events get detected.
#217

You can enable debugging like so:
TEXTWORLD_DEBUG=1 tw-play --hint your_game.ulx

[sultanalnahian]

I think you need _asking instead of _ask in the last section of the Inform7 ask command.

commands {
        ....
            ask/pr :: "ask the {pr} about the bank robbery" :: "_ask the {pr} about the bank robbery";
        }

I just create a PR that will enable you to see what Inform7 events get detected.
#217

You can enable debugging like so:
TEXTWORLD_DEBUG=1 tw-play --hint your_game.ulx

I have corrected _ask to _asking. But still it is not working.

[MarcCote]

Do you have the list of i7_events detected when you try the ask command? You need to reinstall textworld from the master branch first.
pip install -U https://github.com/microsoft/TextWorld/archive/master.zip

[MarcCote]

I played around with the code snippet you shared. I was able to make the ask action appears only once. Here's my test file and the content of the .twl file.

test_asking.py

import textworld


M = textworld.GameMaker()
R = M.new_room("Room A")
M.set_player(R)

alice = M.new("pr", "Alice")
R.add(alice)

alice.add_property("not_asked")

M.test()

output

-= Room A =-
You arrive in a Room A. A typical kind of place.

There is an Alice on the floor.

> ask the Alice about the bank robbery
[DEBUG] Detected Inform7 events:
['_asking the Alice']

the Alice has given the information. he said go north.

> attack Alice
[DEBUG] Detected Inform7 events:
['_attacking the Alice']

the Alice is being attacked.

> attack Alice
[DEBUG] Detected Inform7 events:
['_attacking the Alice']

the Alice is being attacked.

>

person.twl

# person
type pr : t{
    predicates {
        attacked(pr);
        asked(pr);
	    not_asked(pr);
    }
    rules {
        attack/pr   :: $at(P, r) & $at(pr, r) -> attacked(pr);
        ask/pr :: $at(P, r) & $at(pr,r) & not_asked(pr) -> asked(pr);
    }
    constraints {
    # Predicate conflicts
    	pr1 :: asked(pr) & not_asked(pr) -> fail();
    }
    inform7 {
        type {
            kind :: "person";
            definition :: "Person can be attacked. Person can be asked. Person is fixed in place.";
        }

        predicates {
            attacked(pr) :: "The {pr} is attacked";
            asked(pr) :: "The {pr} is asked";
            not_asked(pr) :: "The {pr} is not asked";
        }

        commands {
            attack/pr :: "attack {pr}" :: "_attacking the {pr}";
            ask/pr :: "ask the {pr} about the bank robbery" :: "_asking the {pr}";
        }
	code :: """
            Understand the command "attack" as something new.
            Understand "attack [someone]" as _attacking.
            _attacking is an action applying to a thing.

            After _attacking a person:
		        say "[the noun] is being attacked.";

            Understand the command "ask" as something new.
            Understand "ask [someone] about [text]" as _asking.
            _asking is an action applying to a thing and one topic.

            After _asking a person:
		        say "[the noun] has given the information. he said go north.";
           """;
    }
}

[sultanalnahian]

It is working now. So the only change is in the command definition of ask/pr. Changing "_asking the {pr} about the bank robbery" to "_asking the {pr}", makes it working.

Thank you very much for helping me.

[MarcCote]

Do not hesitate if you have other questions.