17. The system of claim 16 , wherein the postprocessing component is further configured to calculate the similarity between the first item and the second item by distinguishing a reliability of different patterns.
16. The system of claim 14 , wherein the postprocessing component is further configured to sort a first item from the plurality of topics according to an importance score, the importance score being used to rank a first item higher than a second item if: an average similarity between the first item and other items is higher than a similarity between the first item and the second item; or a similarity of the first item to a predefined pattern is higher than a similarity between the second item and the predefined pattern.