Let me add some words about sentence fusion. A human is given two sentences and asked to produce a single coherent sentence that contains only the important information from the original two. This is a highly constrained summarization task. Investigations — carried out by Hal Daume and Daniel Marcu — has shown "that even at this restricted level, there is no measurable agreement between humans regarding what information should be considered important."
Source: tatoeba (1849495)