define
  person sub entity,
    owns name,
    owns age,
    plays friendship:friend;

  name sub attribute,
    value string;

  age sub attribute,
    value long;

  friendship sub relation,
    relates friend;

insert
  $p1 isa person, has name "Alice", has age 30;
  $p2 isa person, has name "Bob", has age 25;
  (friend: $p1, friend: $p2) isa friendship;

match
  $x isa person, has name $n;
get $n;