8. The computer-implemented method of claim 7 , further comprising: determining the respective significance value associated with the respective stem identified in the description.
8. The computer-implemented method of claim 7 , further comprising: determining the respective significance value associated with the respective stem identified in the description. 9. The computer-implemented method of claim 8 , wherein the determining the respective significance value comprises: calculating s ⁡ ( d ′ ) = 1 1 + e α + β · p ⁡ ( d ′ ) , where α and β are predetermined values used to map a frequency in a corpus of the description stem d′ to the respective significance value and p(d′) is the frequency of the description stem d′ in the corpus.