Task: Question Answering
Input (English): Three incremental levels of document preprocessing are experimented with: raw text, text cleaning through document logical structure detection, and removal of keyphrase sparse sections of the document. In doing so, we present the first consistent comparison of different keyphrase extraction models and study their robustness over noisy text. 
 Question: what levels of document preprocessing are looked at?
Output (English): raw text text cleaning through document logical structure detection removal of keyphrase sparse sections of the document