title: Text Summarization Evaluation - BLEU vs ROUGE
body: <p>With the results of two different summary systems (sys1 and sys2) and the same reference summaries, I evaluated them with both BLEU and ROUGE. The problem is: All ROUGE scores of sys1 was higher than sys2 (ROUGE-1, ROUGE-2, ROUGE-3, ROUGE-4, ROUGE-L, ROUGE-SU4, ...) but the BLEU score of sys1 was less than the BLEU score of sys2 (quite much).</p>
  <p>So my question is: Both ROUGE and BLEU are based on n-gram to measure the similar between the summaries of systems and the summaries of human. So why there are differences in results of evaluation like that? And what's the main different of ROUGE vs BLEU to explain this issue?</p>