implication.n3

@prefix : <urn:example:> .

:Alice :likes :Cats ;
       :plays :Piano .

# A material implication works like an if->then
#    P -> Q
# If P then Q
{
    ?Person :plays :Piano .
}
=>
{
    ?Person :likes :Music .
} .

# A converse implication works like a kind of a definition 
#     P <- Q
# Not Q without P 
{
    ( ?X ?Y ) :likesXplaysY ?Person .
}
<=
{
    ?Person :likes ?X .
    ?Person :plays ?Y .
} .

# This converse implication you can use now in other rules
# Find out what Alice likes and plays
{
    ( ?X ?Y ) :likesXplaysY :Alice .
}
=> 
{
    :Alice :does ( ?X ?Y ).  

    # :Alice :does ( :Cats :Piano )
    # :Alice :does ( :Music :Piano ) #(because of the first rule)
} .

# Or in other query
# What does Alice do besides playing piano?
{
    ( ?X :Piano ) :likesXplaysY :Alice .
}
=> 
{
    :Alice :doesPianoAnd ?X .

    # :Alice :doesPianoAnd :Cats 
    # :Alice :doesPianoAnd :Music #(because of the first rule)
} .

# Or 
# Who does play the piano and likes What
{
    ( ?What :Piano ) :likesXplaysY ?Who .
}
=> 
{
    ?Who :doesPianoAnd2 ?What .

    # :Alice :doesPianoAnd2 :Cats 
    # :Alice :doesPianoAnd2 :Music #(because of the first rule)
} .

# Test 
{
    :Alice :does ( :Cats :Piano ) , ( :Music :Piano ) ;
        :doesPianoAnd :Cats , :Music ;
        :doesPianoAnd2 :Cats , :Music .
}
=>
{
    :test :is true .
} .