In written English, certain types of NP-extraposition require a comma before or after the extraposed noun phrase: Because any predicative noun phrase could be used in this manner, this construction is also potentially problematic for the coverage of our grammar and lexicon.
the fact that a comma is required allows us to use a small number of binary type-changing rules (which do not project any dependencies), such as: The translation algorithm presumes that the trees in the Penn Treebank map directly to the desired CCG derivations.