Week 7 Reading Notes: Relevance feedback and query expansion

1.       The issue of synonymy: impact on the recall of most information retrieval systems.

Solution: Query refinement,automatically or user in the loop

(1)     Global methods include:

• Query expansion/reformulation with a thesaurus or WordNet

• Query expansion via automatic thesaurus generation

• Techniques like spelling correction

(2)     Local methods adjust a query relative to the documents that initially appear to match the query. The basic methods here are:

• Relevance feedback

• Pseudo relevance feedback, also known as Blind relevance feedback

2.       Relevance feedback (RF): involve the user in the retrieval process so as to improve the final result set.

(1)     Basic procedure:

• The user issues a (short, simple) query.

• The system returns an initial set of retrieval results.

• The user marks some returned documents as relevant or nonrelevant.

• The system computes a better representation of the information need based on the user feedback.

• The system displays a revised set of retrieval results.

(2)     The Rocchio algorithm

(3)     very effective at improving relevance of results