Mahidol University Logo
Faculty of ICT, Mahidol University
 

Admissions

Printable Version

 

QUERY EXPANSION USING LOCAL CONTEXT ANALYSIS

 

TITLE QUERY EXPANSION USING LOCAL CONTEXT ANALYSIS.
AUTHOR APICHART PHUNCHAROENPONG
DEGREE MASTER OF SCIENCE PROGRAMME IN COMPUTER SCIENCE
FACULTY FACULTY OF SCIENCE
ADVISOR DAMRAS WONGSAWANG
CO-ADVISOR SUPACHAI TANGWONGSAN
 
ABSTRACT
Information Retrieval (IR) is concerned with locating documents that are relevant to the user’s information needs or queries from a large collection of documents. A fundamental problem for information retrieval is word mismatch. A query is usually a short and incomplete description of the underlying information needed. The users of IR systems and the authors of the documents often use different words to refer to the same concept. Most users have no skill in selecting good search terms. This thesis investigated text analysis technique, Local Context Analysis using Weighted Inverse Document Frequency (LCAWIDF), and applied a query expansion technique for Thai text retrieval. We simulated the test environments and compared the results between the LCAWIDF and the original model, Local Context Analysis (LCA) system. The experimental results show that LCAWIDF provides precision and recall improvement over the LCA system. Factors that affect retrieval improvement were studied. These factors are: the number of expanding terms, the percentage of top ranked documents, the number of passages used and passage size. We found that when increasing the number of expanding terms, the recall improvement increased while the precision improvement decreased. The appropriate value of percentage of top ranked documents is 30%. Optimal retrieval efficiency was found when over ten passages at 300 words each, were used.
KEYWORD INFORMATION RETRIEVAL / QUERY EXPANSION / LOCAL CONTEXT ANALYSIS / WEIGHTED INVERSE DOCUMENT FREQUENCY

 

Go to Top

 

ICT Building, Mahidol University, 999 Phuttamonthon 4 Road, Salaya, Nakhonpathom 73170 Tel. +66 02 441-0909 Fax. +66 02 849-6099
Mahidol University Computing Center, The Faculty of ICT, Mahidol University , Rama 6 Road, Rajathevi, Bangkok 10400 Tel. +66 02 354-4333 Fax. +66 02 354-7333