Retrieving semantically equivalent questions is a challenging task due to two main factors: (1) the same question can be rephrased in many different ways; and (2) two questions may be different but may refer implicitly to a common problem with the same answer.
traditional similarity measures based on word overlap such as shingling and Jaccard coefficient (Broder, 1997) and its variations (Wu et al., 2011) are not able to capture many cases of semantic equivalence.