Improving Information Retrieval in MEDLINE by Modulating MeSH Term Weights

1. NLDB 2004 Improving Information Retrieval in MEDLINE by Modulating MeSH Term Weights Kwangcheol Shin, Sang-Yong Han School of CSE, Chung-Ang Univ. Seoul, Korea

2. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

3. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

4. MEDLINE and MeSH • MEDLINE is a premier bibliography database of National Library of Medicine (NLM). • Medical Subject Headings (MeSH) is the authority list of controlled vocabulary terms used for subject analysis of biomedical literature at NLM. • Expert annotators of the NLM assign MeSH keywords to each MEDLINE document for effective retrieval. • Manual annotation with MeSH terms is a distinctive feature of MEDLINE. • MEDLINE is supplied with its own Boolean model-based search engine.

5. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

6. Vector Space Model • In the VSM, the documents are represented as vectors with the coordinates proportional to the number of occurrences. • The similarity between two vectors is measured using the cosine measure:

7. Suggested Method • We show that applying a Vector Space Model-based search engine to MEDLINE data gives much better results than Boolean-based. • More importantly, balancing the weights of the manually assigned MeSH keywords and the text words further improves the quality of the results.

8. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

9. Modulating MeSH Term Weights • MEDLINE documents contain MeSH keywords • Our idea is to increase the weights of MeSH terms in each documents vector.

10. Modulating MeSH Term Weights • We use following procedure 1. Assign the weights wij as in vector space model 2. Use formula to increase the weight of MeSH terms: where ρ is a parameter regulating the sensitivity of the formula to the MeSH terms

12. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

13. Experimental Results - Test Collection • Experimented with the well-known Cystic Fibrosis (CF) reference collection, which is a subset of MEDLINE. • It has 1,239 medical data records supplied with 100 queries with relevant documents provided.

14. Experimental Results

15. Results: Vector Space Model

16. Results: Boolean vs. Vector

17. Contents • MEDLINE and MeSH • Vector Space Model • Modulating MeSH Term Weights • Experimental Results • Conclusion

18. Conclusions • Vector space model gives better results than Boolean model-based system. • Increasing the weights for MeSH terms as compared with the standard vector space model improves retrieval accuracy. • Optimal weights are balanced: both MeSH terms and text terms are taken into account • We get as much as 2.4 times better results than the system currently provided with MEDLINE.

19. Thank you!