They make up the class of Semantic Clue Elements.
( They ( ( ( make up ) ( ( the class ) ( of ( Semantic ( Clue Elements ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP make) (PRT (RP up)) (NP (NP (DT the) (NN class)) (PP (IN of) (NP (NNP Semantic) (NNP Clue) (NNP Elements))))) (. .)))
Semantic Clue elements are a special-case class.
( ( Semantic ( Clue elements ) ) ( ( are ( a ( special-case class ) ) ) . ) )
(ROOT (S (NP (NNP Semantic) (NNP Clue) (NNS elements)) (VP (VBP are) (NP (DT a) (JJ special-case) (NN class))) (. .)))