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Worst case optimal unionintersection expression evaluation
 In Proceedings of the 32nd International Colloquium on Automata, Languages and Programming (ICALP ’05), volume 3580 of Lecture Notes in Computer Science
, 2005
"... addresses: ..."
Latent Semantic Indexing Model for Boolean Query Formulation
, 2000
"... A new model named Boolean Latent Semantic Indexing model based on the Singular Value Decomposition and Boolean query formulation is introduced. While the Singular Value Decomposition alleviates the problems of lexical matching in the traditional information retrieval model, Boolean query formulation ..."
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A new model named Boolean Latent Semantic Indexing model based on the Singular Value Decomposition and Boolean query formulation is introduced. While the Singular Value Decomposition alleviates the problems of lexical matching in the traditional information retrieval model, Boolean query formulation can help users to make precise representation of their information search needs. Retrieval experiments on a number of test collections seem to show that the proposed model achieves substantial performance gains over the Latent Semantic Indexing model.
MAYA: A Fast Questionanswering System Based On A Predictive Answer Indexer
"... We propose a Questionanswering (QA) system in Korean that uses a predictive answer indexer. The predictive answer indexer, first, extracts all answer candidates in a document in indexing time. Then, it gives scores to the adjacent content words that are closely related with each answer cand ..."
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We propose a Questionanswering (QA) system in Korean that uses a predictive answer indexer. The predictive answer indexer, first, extracts all answer candidates in a document in indexing time. Then, it gives scores to the adjacent content words that are closely related with each answer candidate. Next, it stores the weighted content words with each candidate into a database. Using this technique, along with a complementary analysis of questions, the proposed QA system can save response time because it is not necessary for the QA system to extract answer candidates with scores on retrieval time. If the QA system is combined with a traditional Information Retrieval system, it can improve the document retrieval precision for closedclass questions after minimum loss of retrieval time.
A Reliable Indexing Method for a Practical QA System
, 2002
"... We propose a fast and reliable Questionanswering (QA) system in Korean, which uses a predictive answer indexer based on 2pass scoring method. The indexing process is as follows. The predictive answer indexer first extracts all answer candidates in a document. Then, using 2pass scoring method, it ..."
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We propose a fast and reliable Questionanswering (QA) system in Korean, which uses a predictive answer indexer based on 2pass scoring method. The indexing process is as follows. The predictive answer indexer first extracts all answer candidates in a document. Then, using 2pass scoring method, it gives scores to the adjacent content words that are closely related with each answer candidate. Next, it stores the weighted content words with each candidate into a database. Using this technique, along with a complementary analysis of questions, the proposed QA system saves response time and enhances the precision.
Efficient Evaluation of Set Expressions
, 2014
"... In this thesis, we study the problem of evaluating set expressions over sorted sets in the comparison model. The problem arises in the context of evaluating search queries in text database systems; most text search engines maintain an inverted list, which consists of a set of documents that contai ..."
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In this thesis, we study the problem of evaluating set expressions over sorted sets in the comparison model. The problem arises in the context of evaluating search queries in text database systems; most text search engines maintain an inverted list, which consists of a set of documents that contain each possible word. Thus, answering a query is reduced to computing the union, the intersection, or a more complex set expression over sets of documents containing the words in the query. At the first step, for a given expression on a number of sets and the sizes of the sets, we investigate the worstcase complexity of evaluating the expression in terms of the sizes of the sets. We prove lower bounds and provide algorithms with the matching running time up to a constant factor. We then refine the problem further and design an algorithm that computes such expressions according to the degree by which the input sets are interleaved rather than only considering sets sizes. We prove the optimality of our algorithm by way of presenting a matching lower bound sensitive to the interleaving measure. The algorithms we present are different in the set of set operators they allow in input expressions. We provide algorithms that are worstcase optimal for inputs with union, intersection, and symmetric difference operators. One of the algorithms we provide also supports minus and complement operators and is conjectured to be optimal when an input is allowed to contain these operators as well. We also provide a worstcase optimal algorithm for the form of problem where the input may contain “threshold ” operators, which generalize union and intersection operators: for a number t, a tthreshold operator selects elements that appear in at least in t of the operand sets. Finally, the adaptive algorithm we provide supports union and intersection operators.