# Counting dogs for a license rule
#
# Alice owns five dogs and Bob owns two. Scoped collection counts each
# person's distinct dogs, and an N3 rule derives a license requirement when
# the count exceeds four.

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

:alice :hasDog :dog1, :dog2, :dog3, :dog4, :dog5 .
:bob :hasDog :dog6, :dog7 .

{
    ?person :hasDog ?anyDog .
    (
        ?dog {
            ?person :hasDog ?dog
        }
        ?dogs
    ) log:collectAllIn ?SCOPE .
    ?dogs list:length ?count .
} => {
    ?person :dogCount ?count
} .

{
    ?person :dogCount ?count .
    ?count math:greaterThan 4
} => {
    ?person :mustHave :dogLicense
} .