PredicatePreference.n3

PREFIX e: <http://eulersharp.sourceforge.net/2003/03swap/log-rules#>
PREFIX ex: <https://example.org/tmp#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX list: <http://www.w3.org/2000/10/swap/list#>
PREFIX schema: <http://schema.org/>

# Profile document
<https://ruben.verborgh.org/profile/#me>
  a foaf:Person;
  foaf:nick "RV";
  foaf:givenName "Ruben";
  foaf:name "Ruben Verborgh".


# Default greeting preference
ex:defaultGreetingPreference a ex:PredicatePreference;
  # Ordered preference of predicates
  ex:preferredPredicates (
    foaf:nick
    foaf:givenName
    foaf:name
    schema:givenName
  );
  # Name of the predicate into which the result is put
  ex:resultPredicate ex:preferredGreeting.


# Apply predicate preferences
{
  # Load the applicable preference
  ?predicatePreference
    ex:preferredPredicates ?predicates;
    ex:resultPredicate ?resultPredicate.

  # Find all subjects that use predicates occurring in the preference
  ?predicates list:member ?selectedPredicate.
  ?subject ?selectedPredicate ?preferredValue.

  # Ensure no better match exists earlier in the preference list
  (?head ?after) list:append ?predicates.
  (?before (?selectedPredicate)) list:append ?head.
  ?scope e:findall (
    ?candidate
    {
      ?candidate list:in ?before.
      ?subject ?candidate ?value.
    }
    ()
  ).
}
=>
{
  ?subject ?resultPredicate ?preferredValue.
}.