Signature file hashing using term occurrence and query frequencies

Signature files act as a filter on retrieval to discard a large number of nonqualifying data items. Linear hashing with superimposed signatures (LHSS) provides an effective retrieval filter to process queries in dynamic databases. This study is an analysis of the effects of reflecting the term occurrence and query frequencies to signatures in LHSS. This approach relaxes the unrealistic uniform frequency assumption and lets the terms with high discriminatory power set more bits in signatures. The simulation experiments based on the derived formulas explore the amount of page savings with different occurrence and query frequency combinations at different hashing levels. The results show that the performance of LHSS improves with the hashing level and the larger the difference between the term discriminatory power values of the terms, the higher the retrieval efficiency. The authors also discuss the benefits of this approach to alleviate the imbalance between the levels of efficiency and relevancy in the unrealistic uniform frequency assumption case