On Identifying Phrases Using Collection Statistics.

The use of phrases as part of similarity computations can enhance search effectiveness. But the gain comes at a cost, either in terms of index size, if all word-tuples are treated as queryable objects; or in terms of processing time, if postings lists for phrases are constructed at query time. There is also a lack of clarity as to which phrases are “interesting”, in the sense of capturing useful information. Here we explore several techniques for recognizing phrases using statistics of large-scale collections, and evaluate their quality.