3. The system of claim 1 , wherein the ranking algorithm can rank a generated snippet by: 
 rank= w s c w +p s c p +P s c p +n s c n +r s c r , wherein, w s represents the number of words in the generated snippet, p s represents the number of punctuation symbols in the generated snippet, P s represents a subset of p s , which corresponds to particular punctuation symbols in the generated snippet, n s represents the number of numbers in the generated snippet, r s represents a score of the proximity feature associated with the generated snippet, and c w , c p , c n , and c r represent tunable coefficients associated with each ranking parameter.
3. The system of claim 1 , wherein the ranking algorithm can rank a generated snippet by: 
 rank= w s c w +p s c p +P s c p +n s c n +r s c r , wherein, w s represents the number of words in the generated snippet, p s represents the number of punctuation symbols in the generated snippet, P s represents a subset of p s , which corresponds to particular punctuation symbols in the generated snippet, n s represents the number of numbers in the generated snippet, r s represents a score of the proximity feature associated with the generated snippet, and c w , c p , c n , and c r represent tunable coefficients associated with each ranking parameter. 4. The system of claim 3 , wherein the proximity feature is associated with a generated snippet span and a score of the span can be calculated by: 
 score of the span= f ×2 2t−l wherein, f is defined as a tunable proximity factor, t is defined as a number of query terms in the span, and l is a number of terms in the span.