Probabilistic structured query methods

Structured methods for query term replacement rely on separate estimates of term tes of replacement probabilities. Statistically significantfrequency and document frequency to compute a weight for each query term. This paper reviews prior work on structured query techniques and introduces three new variants that leverage estima improvements in retrieval effectiveness are demonstrated for cross-language retrieval and for retrieval based on optical character recognition when replacement probabilities are used to estimate both term frequency and document frequency.