prefix : <http://example.org/>
prefix schema: <http://schema.org/>

:a schema:name  "Alice" ;
   schema:knows :a, :b  .

:b schema:name  "Bob"   ;
   schema:knows :c      .

:c schema:name  "Carol" .

:d schema:name  23      .  # Should fail

:e schema:name  "Emily" ;  # Should fail
   schema:knows :d      .

:f schema:name "Frank"  ;
   :status     :Walking .
