16. The method of claim 14 , further comprising: sorting the opinion data of the target domain into groups based at least in part on the occurrence of a particular identifier in the opinion data, wherein the particular identifier is labeled with a known sentiment; creating an additional identifier based at least in part on the occurrence of a term that is used a predefined number of times in one of the groups; and assigning the known sentiment to the additional identifier.
16. The method of claim 14 , further comprising: sorting the opinion data of the target domain into groups based at least in part on the occurrence of a particular identifier in the opinion data, wherein the particular identifier is labeled with a known sentiment; creating an additional identifier based at least in part on the occurrence of a term that is used a predefined number of times in one of the groups; and assigning the known sentiment to the additional identifier. 17. The method of claim 16 , further comprising assigning a first weight to the identifiers and a second weight to the additional identifier.