@prefix : <http://example.org#>.

# facts
:tweety a :Penguin.

# Penguin implies Bird
{
    ?X a :Penguin.
} => {
    ?X a :Bird.
}.

# Penguins cannot fly (negation)
{
    ?X a :Penguin.
    ?X :can :fly.
} => ($ $).

# Birds can fly or are penguins (disjunction)
{
    ?X a :Bird.
} => ($ {
    ?X :can :fly.
} {
    ?X a :Penguin.
} $).

# goal: prove that tweety cannot fly
{
    {
        :tweety :can :fly.
    } => ($ $).
} =^ {
    {
        :tweety :can :fly.
    } => ($ $).
}.
