13. The system of claim 12 , wherein the operations further comprise determining that the first snippet is insufficient and in response: selecting a snippet piece to append to the first snippet, determining that the snippet piece is to be appended to the first snippet, and appending the snippet piece to the first snippet.
13. The system of claim 12 , wherein the operations further comprise determining that the first snippet is insufficient and in response: selecting a snippet piece to append to the first snippet, determining that the snippet piece is to be appended to the first snippet, and appending the snippet piece to the first snippet. 15. The system of claim 13 , wherein appending the snippet piece to the first snippet comprises removing a previously appended snippet piece from the first snippet piece and appending the snippet piece to the first snippet.