Axiomatic analysis of smoothing methods in language models for pseudo-relevance feedback

Pseudo-Relevance Feedback (PRF) is an important general technique for improving retrieval effectiveness without requiring any user effort. Several state-of-the-art PRF models are based on the language modeling approach where a query language model is learned based on feedback documents. In all these models, feedback documents are represented with unigram language models smoothed with a collection language model. While collection language model-based smoothing has proven both effective and necessary in using language models for retrieval, we use axiomatic analysis to show that this smoothing scheme inherently causes the feedback model to favor frequent terms and thus violates the IDF constraint needed to ensure selection of discriminative feedback terms. To address this problem, we propose replacing collection language model-based smoothing in the feedback stage with additive smoothing, which is analytically shown to select more discriminative terms. Empirical evaluation further confirms that additive smoothing indeed significantly outperforms collection-based smoothing methods in multiple language model-based PRF models.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Computer Science

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2016

Author dc:creator

• Hazimeh, Hussein

Contributors dc:contributor

• Zhai, ChengXiang

• Search Engines
• Text Retrieval
• Relevance Feedback
• Pseudo-Relevance Feedback
• Implicit Feedback
• Blind Feedback

Statement dc:rights

• Copyright 2016 Hussein Hazimeh

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/92709

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/92709