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

# facts
{
    :ground :is :wet.
} => ($ $).

# if it's raining, then the ground is wet
{
    :sky :has :rain.
} => {
    :ground :is :wet.
}.

# goal: prove that it is not raining
{
    {
        :sky :has :rain.
    } => ($ $).
} =^ {
    {
        :sky :has :rain.
    } => ($ $).
}.
