Mining question patterns based on question clusters is motivated by the observation that, all questions within a QC tend to ask questions about an identical "question topic" (e.g., nyc in the above example) from different aspects, or the same aspect but using different expressions.
we can leverage the consensus information among questions to detect the boundary of the question topic: the more times an n-gram occurs in different questions within a question cluster, the more likely it is the question topic of the current question cluster.