The role of multi-word units in interactive information retrieval

The paper presents several techniques for selecting noun phrases for interactive query expansion following pseudo-relevance feedback and a new phrase search method. A combined syntactico-statistical method was used for the selection of phrases. First, noun phrases were selected using a part-of-speech tagger and a noun-phrase chunker, and secondly, different statistical measures were applied to select phrases for query expansion. Experiments were also conducted studying the effectiveness of noun phrases in document ranking. We analyse the problems of phrase weighting and suggest new ways of addressing them. A new method of phrase matching and weighting was developed, which specifically addresses the problem of weighting overlapping and non-contiguous word sequences in documents.