nested_implication.n3

@prefix : <urn:example:> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .

:Light :is :Green .

:Renault a :Car ;
    :is :Waiting .

# Nesting an implies rule in the conclusion is like providing a guard
# in the premisse.
#
#  IF (Light is Green):
#     IF ( C a Car AND C is Waiting ): C is Driving          #1
#     IF ( P a Person AND P is Waiting ): P is StillWaiting  #2
#
# Rule number #1 still gets fired even when there is no Person (waiting) 
{
    :Light :is :Green .
}
=>
{
    { ?C a :Car . ?C :is :Waiting } => { ?C :is :Driving } .
    { ?P a :Person . ?P :is :Waiting } => { ?P :is :StillWaiting } .
} .

# Nesting a implies rule in the premisse is like matching a rule
#
# IF EXISTS_RULE("IF (P a Person AND P is Waiting) : P is StillWaiting"):
#     GreenLightRule is true 
{
   { ?P a :Person . ?P :is :Waiting } => { ?P :is :StillWaiting } . 
}
=>
{
    :GreenLightRule :is true .
} .

# Test
{
    :Renault :is :Driving .
    :GreenLightRule :is true .
}
=>
{
    :test :is true .
} .