Masatoshi Yoshikawa

Adaptive web search based on user profile constructed without any effort from users

Web search engines help users find useful information on the World Wide Web (WWW). However, when the same query is submitted by different users, typical search engines return the same result regardless of who submitted the query. Generally, each user has different information needs for his/her query. Therefore, the search result should be adapted to users with different information needs. In this paper, we first propose several approaches to adapting search results according to each users need for relevant information without any user effort, and then verify the effectiveness of our proposed approaches. Experimental results show that search systems that adapt to each users preferences can be achieved by constructing user profiles based on modified collaborative filtering with detailed analysis of users browsing history in one day.

XRel : A path-based approach to storage and retrieval of XML documents using relational databases

This article describes XRel, a novel approach for storage and retrieval of XML documents using relational databases. In this approach, an XML document is decomposed into nodes on the basis of its tree structure and stored in relational tables according to the node type, with path information from the root to each node. XRel enables us to store XML documents using a fixed relational schema without any information about DTDs and also to utilize indices such as the B+-tree and the R-tree supported by database management systems. Thus, XRel does not need any extension of relational databases for storing XML documents. For processing XML queries, we present an algorithm for translating a core subset of XPath expressions into SQL queries. Finally, we demonstrate the effectiveness of this approach through several experiments using actual XML documents.

FTW: fast similarity search under the time warping distance

Time-series data naturally arise in countless domains, such as meteorology, astrophysics, geology, multimedia, and economics. Similarity search is very popular, and DTW (Dynamic Time Warping) is one of the two prevailing distance measures. Although DTW incurs a heavy computation cost, it provides scaling along the time axis. In this paper, we propose FTW (Fast search method for dynamic Time Warping), which guarantees no false dismissals in similarity query processing. FTW efficiently prunes a significant number of the search cost. Experiments on real and synthetic sequence data sets reveals that FTW is significantly faster than the best existing method, up to 222 times.

QRS: a robust numbering scheme for XML documents

Update management of XML documents is an increasingly important research issue in XML databases, because contents of XML documents evolve as time goes by. Even though, XML databases should be able to effectively process XML queries as well as updates on the documents. We propose a robust node-numbering scheme for XML documents named QRS (quartering-regions scheme). In QRS, reefs (regions expressed by floating-point numbers), a variant of regions, are used for expressing node-numbers. Reefs are almost compatible to regions, and thus they can be used for detecting ancestor-descendant relationship among nodes for the purpose of efficient query processing. Moreover, reefs can cope with updates by utilizing gaps between reefs in terms of floating-point numbers. Consequently, we can avoid node renumbering as much as possible.

Schema virtualization in object-oriented databases

A description is given of the concept and implementation techniques of schema virtualization in object-oriented databases. The objective of schema virtualization is to provide users with multiple views of a database. First, the notions of virtual classes and virtual schemata, which are natural extension of views in relational databases, is introduced. Then, procedures to convert a schema into a virtual one, as well as rules schemata and their conversion should satisfy, are discussed. The key issue of the design of virtual classes and virtual schemata is regarding procedures as objects. Closure properties of classes and schemata are also discussed. Finally, several implementation techniques for realizing schema virtualization in Smalltalk-80 are presented.<<ETX>>

An efficiently updatable index scheme for structured documents

We propose an efficiently updatable index scheme for XML documents. This index scheme consists of four types of indices. Content index manages occurrence positions of words, element names, attribute names and attribute values. Local structure index manages logical structure of each document. Global structure index summarizes logical structure of document instances for a DTD. The last one is called structure meta index, and keeps, for each element, the number of local structure indices and global structure indices which include the element. Using our four types of indices, therefore, a wide range of queries over structured documents can be processed efficiently. We compare our indices with existing indices in terms of index size, update cost and retrieval cost.

Refinement of TF-IDF schemes for web pages using their hyperlinked neighboring pages

In IR (information retrieval) systems based on the vector space model, the TF-IDF scheme is widely used to characterize documents. However, in the case of documents with hyperlink structures such as Web pages, it is necessary to develop a technique for representing the contents of Web pages more accurately by exploiting the contents of their hyperlinked neighboring pages. In this paper, we first propose several approaches to refining the TF-IDF scheme for a target Web page by using the contents of its hyperlinked neighboring pages, and then compare the retrieval accuracy of our proposed approaches. Experimental results show that, generally, more accurate feature vectors of a target Web page can be generated in the case of utilizing the contents of its hyperlinked neighboring pages at levels up to second in the backward direction from the target page.

Learning Bilingual Translations from Comparable Corpora to Cross-Language Information Retrieval: Hybrid Statistics-based and Linguistics-based Approach

Recent years saw an increased interest in the use and the construction of large corpora. With this increased interest and awareness has come an expansion in the application to knowledge acquisition and bilingual terminology extraction. The present paper will seek to present an approach to bilingual lexicon extraction from non-aligned comparable corpora, combination to linguistics-based pruning and evaluations on Cross-Language Information Retrieval. We propose and explore a two-stages translation model for the acquisition of bilingual terminology from comparable corpora, disambiguation and selection of best translation alternatives on the basis of their morphological knowledge. Evaluations using a large-scale test collection on Japanese-English and different weighting schemes of SMART retrieval system confirmed the effectiveness of the proposed combination of two-stages comparable corpora and linguistics-based pruning on Cross-Language Information Retrieval.

A Data Model for Temporal XML Documents

XML is expected to become the next generation standard language for exchanging data over the Internet. In general, the contents of XML documents may change as time goes by, and then, it is important to capture entire histories of those documents. In this paper, we propose a logical data model for representing histories of XML documents. The proposed model extends the XPath data model, and is capable of representing change histories of XML documents. Various alternative approaches to the physical implementation of the model are also presented.

Bilingual Terminology Acquisition from Comparable Corpora and Phrasal Translation to Cross-Language Information Retrieval

The present paper will seek to present an approach to bilingual lexicon extraction from non-aligned comparable corpora, phrasal translation as well as evaluations on Cross-Language Information Retrieval. A two-stages translation model is proposed for the acquisition of bilingual terminology from comparable corpora, disambiguation and selection of best translation alternatives according to their linguistics-based knowledge. Different rescoring techniques are proposed and evaluated in order to select best phrasal translation alternatives. Results demonstrate that the proposed translation model yields better translations and retrieval effectiveness could be achieved across Japanese-English language pair.