sentence1: word ordering is the abstract language modeling task of making a grammatical sentence by ordering a bag of words ( white , 2004 ; zhang and clark , 2015 ; de gispert et al. , 2014 ; bohnet et al. , 2010 ; filippova and strube , 2007 ; he et al. , 2009 ) , which is practically relevant to text-to-text applications such as summarization ( cite-p-11-3-2 ) and machine translation ( cite-p-11-1-1 ) .
sentence2: word ordering is a fundamental problem in nlp and has been shown to be np-complete in discourse ordering ( cite-p-16-1-1 ) and in smt with arbitrary word reordering ( cite-p-16-3-6 ) .