... frequent words F to generalizewords to word classes”. We define a word classas either a word itself or its part of speech. Givena sentence s = w1, w2, . . . , w|s|, where wiis thei-th word ... order of symbols like in word/ phoneme lat-tices, and nodes are clusters of salient words ag-gregated using synonymy, similarity, or subtreesof a thesaurus. However, salient word selectionand aggregation ... where wiis thei-th word of s, we generalize its words wito word classes ωias follows:ωi=wiif wi∈ FP OS(wi) otherwisethat is, a word wiis left unchanged if it occursfrequently...