Faculty Profiles - ISHIKAWA, Yoshiharu

Papers - ISHIKAWA, Yoshiharu

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Evaluation of Signature Files as Set Access Facilities in OODBs Reviewed

Yoshiharu Ishikawa, Hiroyuki Kitagawa, and Nobuo Ohbo

Proceedings of the 1993 ACM SIGMOD International Conference on Management of Data (SIGMOD '93) page： 247-256 1993.5

Authorship：Lead author Language：English

Object-oriented database systems (OODBs) need efficient support for manipulation of complex objects. In particular, support of queries involving evaluations of set predicates is often required in handling complex objects. In this paper, we propose a scheme to apply signature file techniques, which were originally invented for text retrieval, to the support of set value accesses, and quantitatively evaluate their potential capabilities. Two signature file organizations, the sequential signature file and the bit-sliced signature file, are considered and their performance is compared with that of the nested index for queries involving the set inclusion operator (subseteq). We develop a detailed cost model and present analytical results clarifying their retrieval, storage, and update costs. Our analysis shows that the bit-sliced signature file is a very promising set access facility in OODBs.

Estimation of False Drops in Set-valued Objects Retrieval with Signature Files Reviewed

Hiroyuki Kitagawa, Yoshiaki Fukushima, Yoshiharu Ishikawa, and Nobuo Ohbo

Proceedings of the Fourth International Conference on Foundations of Data Organization and Algorithms (FODO '93) page： 146-163 1993.10

Language：English

Advanced database systems have to support complex data structures as treated in object-oriented data models and nested relational data models. In particular, efficient processing of set-valued object retrieval (simply, set retrieval) is indispensable for such systems. In the previous paper [6], we proposed the use of signature files as efficient set retrieval facilities and showed their potential capabilities based on a disk page access cost model. Retrieval with signature files is always accompanied by mismatches called false drops, and it is very important in designing signature files to properly control the false drops.
In this paper, we present an in-depth study of false drops in set retrieval with signature files. We derive formulas estimating false drops in four types of set retrieval based on the has-subset, is-subset, has-intersection, and is-equal relationships. Then we evaluate their validity by computer simulations. Simulation study is also done to investigate false drops in practically probable more complex situations.

Analysis of Indexing Schemes to Support Set Retrieval of Nested Objects Reviewed

Yoshiharu Ishikawa and Hiroyuki Kitagawa

Proceedings of the International Symposium on Advanced Database Technologies and Their Integration (ADTI '94) page： 55-62 1994.10

Authorship：Lead author Language：English

Efficient retrieval of nested objects is an important issue in
advanced database systems. So far, many indexing methods for nested objects are proposed. However, they do
not consider retrieval of nested objects based on the set
comparison operators such as subseteq and supseteq. In this paper, we
propose four set access facilities for nested objects and compare their performance in terms of retrieval cost, storage
cost, and update cost. Our analysis shows that a combination of the signature file method and the nested index is
very promising for set retrieval of nested objects

Cost Evaluation of Set-valued Object Retrieval with Signature Files Reviewed

Yoshiharu Ishikawa, Hiroyuki Kitagawa, and Nobuo Ohbo

Journal of IPSJ Vol. 36 ( 2 ) page： 383-395 1995.2

Design and Performance Analysis of Indexing Schemes for Set Retrieval of Nested Objects Reviewed

Yoshiharu Ishikawa and Hiroyuki Kitagawa

IEICE Transactions on Information and Systems Vol. E78-D ( 11 ) page： 1424-1432 1995.11

Language：English Publishing type：Research paper (scientific journal)

Efficient retrieval of nested objects is an important issue in advanced database systems. So far, a number of indexing methods for nested objects have been proposed. However, they do not consider retrieval of nested objects based on the set comparison operators such as subseteq and supseteq. Previouly, we proposed four set access facilities for nested objects and compared their performance in terms of retrieval cost, storage cost, and update cost. In this paper, we extend the study and present refined algorithms and cost formulas applicable to more generalized situations. Our cost models and analysis not only contribute to the study of set-valued retrieval but also to cost estimation of various indexing methods for nested objects in general.

Design and Evaluation of Signature File Organization Incorporating Vertical and Horizontal Decomposition Schemes Reviewed

Hiroyuki Kitagawa, Noriyasu Watanabe, and Yoshiharu Ishikawa

Proceedings of the Seventh International Conference on Database and Expert Systems Applications (DEXA'96) page： 875-888 1996.9

Language：English

Signature files are known as promising facilities to speed up access to large information repositories in database and information retrieval systems. This paper presents a new signature file organization method, named Partitioned Frame-Sliced Signature File (P-FSSF), and studies its performance. P-FSSF incorporates both vertical and horizontal decomposition schemes to reduce page accesses required to look up signatures. In addition, P-FSSF is flexible enough to have its concrete organization tuned to real application environments. We develop formulas to estimate the retrieval cost of P-FSSF in the context of the general set-valued object retrieval. Also, formulas to tell the update and storage costs are derived. Then, the processing cost of P-FSSF is shown to be lower than the other existing signature file organizations in general. We also show that Partitioned Bit-Sliced Signature File (P-BSSF), which is a special case of P-FSSF, is appropriate organization in most probable cases through the study of the optimal parameter values for P-FSSF.

SignatureCache: An Efficient Access Structure for Distributed Mediated Environments Reviewed

Yoshiharu Ishikawa and Shunsuke Uemura

Proceedings of the International Symposium on Cooperative Database Systems for Advanced Applications (CODAS '96) page： 538-541 1996.12

Language：English

To integrate distributed heterogeneous information sources in networked environments, we need efficient facilities to access such information. In this paper, we propose a method called SignatureCache to enable clients to access distributed sources in an efficient manner. The method is based on signature files, a popular indexing method in text retrieval. In our framework, a mediator extracts textual information from each source and generates a signatur---a compact representation of the extracted information. Generated signatures are collected by the mediator and accumulated into a signature file. Each client of the mediator replicates a part of signatures in the signature file during query execution time. The cached signatures can be considered as a special kind of signature file, thus we can utilize them for efficient index lookup at later time. In query processing, we can make use of subsumption relationship between queries and the semantic descriptions for cached signatures to determine whether the required signature entries are locally available or not.

A Wrapping Architecture for IR Systems to Mediate External Structured Document Sources Reviewed

Yoshiharu Ishikawa, Takehiro Furudate, and Shunsuke Uemura

Proceedings of the Fifth International Conference on Database Systems for Advanced Applications (DASFAA '97) page： 431-440 1997.4

Authorship：Lead author Language：English

With the growth of digital libraries and electronic publishing, many structured document sources are appearing and their effective mediation is an important research topic. In this paper, we propose a wrapping architecture for externally maintained structured document sources. Our wrapping target is information retrieval systems (IRSs) that provide access to structured documents. We describe a wrapper construction method for such IRSs with limited functionality. The constructed wrapper enhances retrieval facilities of the underlying IRS and provides an object database view to the mediator. We focus on determining whether the underlying IRS can support a given query. Then we discuss some research issues related to our wrapping architecture.

False Drop Analysis of Set Retrieval with Signature Files Reviewed

Hiroyuki Kitagawa and Yoshiharu Ishikawa

IEICE Transactions on Information and Systems Vol. E80-D ( 6 ) page： 653-664 1997.6

Language：English Publishing type：Research paper (scientific journal)

Modern database systems have to support complex data objects, which appear in advanced data models such as object-oriented data models and nested relational data models. Set-valued objects are basic constructs to build complex structures in those models. Therefore, efficient processing of set-valued object retrieval (simply, set retrieval) is an important feature required of advanced database systems. Our previous work proposed a basic scheme to apply superimposed coded signature files to set retrieval and showed its potential advantages over the B-tree index based approach using a performance analysis model. Retrieval with signature files is always accompanied by mismatches called false drops, and proper control of the false drops is indispensable in the signature file design. This study intensively analyzes the false drops in set retrieval with signature files. First, schemes to use signature files are presented to process set retrieval involving "has-subset," "is-subset," "has-intersection," and "is-equal" predicates, and generic formulas estimating the false drops are derived. Then, three sets of concrete formulas are derived in three ways to estimate the false drops in the four types of set retrieval. Finally, their estimates are validated with computer simulations, and advantages and disadvantages of each set of the false drop estimation formulas are discussed. The analysis shows that proper choice of estimation formulas gives quite accurate estimates of the false drops in set retrieval with signature files.

MindReader: Querying Databases through Multiple Examples Reviewed

Yoshiharu Ishikawa, Ravishankar Subramanya, and Christos Faloutsos

Proceedings of the 24th International Conference on Very Large Data Bases (VLDB '98) page： 218-227 1998.8

Authorship：Lead author Language：English

Users often can not easily express their queries. For example, in a multimedia/image by content setting, the user might want photographs with sunsets; in current systems, like QBIC, the user has to give a sample query, andto specify the relative importance of color, shape and texture. Even worse, the user might want correlations between attributes, like, for example, in a traditional, medical record database, a medical researcher might wantto find "mildly overweight patients", where the implied query would be "weight/height ~ 4 lb/inch".

Our goal is to provide a user-friendly, but theoretically solid method, tohandle such queries. We allow the user to give several examples, and, optionally, their 'goodness' scores, and we propose a novel method to "guess" which attributes are important, which correlations are important, and withwhat weight.

Our contributions are twofold: (a) we formalize the problem as a minimization problem and show how to solve for the optimal solution, completely avoiding the ad-hoc heuristics of the past. (b) Moreover, we are the first that can handle 'diagonal' queries (like the 'overweight' query above). Experiments on synthetic and real datasets show that our method estimates quickly and accurately the 'hidden' distance function in the user's mind.

A Semantic Caching Method Based on Linear Constraints Reviewed

Yoshiharu Ishikawa and Hiroyuki Kitagawa

Proceedings of the 1999 International Symposium on Database Applications in Non-Traditional Environments (DANTE'99) page： 133-140 1999.11

Authorship：Lead author Language：English

Because performance is a crucial issue in database systems, data caching techniques have been studied in database research field, especially in client-server databases and distributed databases. Recently, the idea of semantic caching has been proposed. The approach uses semantic information to describe cached data items so that it tries to exploit not only temporal locality but also semantic locality to improve query response time. In this paper, we propose linear constraint-based semantic caching as a new approach, we describe the semantic information about the cached relational tuples as compact constraint tuples. The focus in this paper is the representation method of cache information and the cache examination algorithm.

A Rule-oriented Architecture to Incorporate Dissemination-based Information Delivery into Information Integration Environments Reviewed

Hironori Mizuguchi, Hiroyuki Kitagawa, Yoshiharu Ishikawa, and Atsuyuki Morishima

Proceedings of East-European Conference on Advances in Databases and Information Systems Held Jointly with International Conference on Database Systems for Advanced Applications (ADBIS-DASFAA 2000) page： 185-199 2000.9

Language：English

Integration of heterogeneous information sources has been one of important research issues in recent advanced application environments. Today, various types of information sources are available. Dissemination-based information delivery services that autonomously deliver information from the server sites to users are among the useful and promising information sources. In this paper, we present incorporation of dissemination-based information delivery into information integration environments. The integration here has two goals: (1) Users can utilize dissemination-based information services as other information sources such as databases and the Web. Namely, they can be sources of information integration. (2) Users can obtain integrated information through dissemination-based delivery. We explain this requirement can be met by a combination of an information integration engine and event-driven rule processing scheme. We also explain prototype system development.

X2QL: An eXtensible XML Query Language Supporting User-defined Foreign Functions Reviewed

Norihide Shinagawa, Hiroyuki Kitagawa, and Yoshiharu Ishikawa

Language：English

With the recent and rapid advance of the Internet, management of structured documents such as XML documents and their databases has become more and more important. A number of query languages for XML documents have been proposed up to the present. Some of them enable tag-based powerful document structure manipulation. However, their contents processing capability is very limited. Here, the contents processing implies the similarity-based selection, ranking, summary generation, topic extraction, and so on, as well as simple string-based pattern matching. In this paper, we propose an extensible XML query language X2QL, which features inclusion of user-defined foreign functions to process document contents in the context of XML-QL-based document structure manipulation. This feature makes it possible to integrate application-oriented high-level contents processing facilities into querying documents. We also describe an implementation of an X2QL query processing systemon top of XSLT processors.

Integration of Spatial Information Sources Based on Source Description Framework Reviewed

Yoshiharu Ishikawa, Gihyong Ryu, and Hiroyuki Kitagawa

Proceedings of the Seventh International Conference on Database Systems for Advanced Applications (DASFAA 2001) page： 160-161 2001.4

Authorship：Lead author Language：English

Recent progress of digital cartography and Internet technologies
enabled new types of services on the network such
as search engines that provide information within some specific
geographic areas and retrieval services which allow
map-oriented query interfaces. We call such services spatial
information sources. In this paper, we propose a framework
to integrate heterogeneous spatial information sources
to provide an integrated view to users. Our main focus is
heterogeneity of spatial information sources―since existing
spatial information sources differ in their contents and
query capabilities, integration of such sources requires an
appropriate framework to describe their contents and query
capabilities. In this paper, we show such a description
framework and illustrate query processing strategies that
utilize source descriptions of spatial information sources.

Algebraic Service Specification and Rule Generation for Integrating Multiple Dissemination-Based Information Systems Reviewed

Hiroyuki Kitagawa, Tomoyuki Kajino, Yoshiharu Ishikawa

Proceedings of the Seventh International Conference on Database Systems for Advanced Applications (DASFAA 2001) page： 344-351 2001.4

Language：English

Integration of heterogeneous information sources has
been one of important data engineering research issues.
Various types of information sources are available today.
They include dissemination-based information sources,
which actively and autonomously deliver information
from server sites to users. We have been developing a
mediator/wrapper-based information integration system, in
which we employ ECA rules to enable users to define new
information delivery services integrating multiple existing
dissemination-based information sources. However, it is
not easy for users to directly specify ECA rules and to verify
them. In this paper, we propose a scheme to specify new
information delivery services using the framework of the
relational algebra. We discuss some important properties
of the specification, and show how we can derive ECA rules
to implement the delivery services.

Querying Geographic Data in XML via Extensible XML Query Language X2QL Reviewed

Norihide Shinagawa, Takayuki Nagai, Hiroyuki Kitagawa, Yoshiharu Ishikawa

Proceedings of Symposium on ASIA GIS 2001 page： (CD-ROM publishing, no page no) 2001.6

Language：English

XML has attracted a great deal of attention as standard data exchange format, and XML representing geographic information such as G-XML has been developed. In near future, geographic data written in XML will be exchanged through the Internet. Therefore, it will become a very important issue to efficiently query geographic data in XML. To query geographic data in XML, spatial operations such as distance calculation and spatial containment test need be provided in query languages. However, in general, XML query languages do not support such spatial operations. This paper illustrates G-XML data can be queried via eXtensible XML Query Language X2QL, which has been developed by our research group. X2QL features inclusion of user-defined foreign functions to introduce application-oriented processing capability. Thus, we can utilize various spatial operations in X²QL as appropriate foreign functions. This paper also describes the development of a prototpye X2QL query processing system.

An On-Line Document Clustering Method Based on Forgetting Factors Reviewed

Yoshiharu Ishikawa, Yibing Chen, and Hiroyuki Kitagawa

Proceedings of the 5th European Conference on Research and Advanced Technology for Digital Libraries (ECDL 2001) page： 332-339 2001.9

Authorship：Lead author Language：English

With the rapid development of on-line information services, information technologies for on-line information processing have been receiving much attention recently. Clustering plays important roles in various on-line applications such as extraction of useful information from news feeding services and selection of relevant documents from the incoming scientific articles in digital libraries. In on-line environments, users generally have interests on newer documents than older ones and have no interests on obsolete old documents. Based on this observation, we propose an on-line document clustering method F2ICM ( Forgetting-Factor-based Incremental Clustering Method) that incorporates the notion of a forgetting factor to calculate document similarities. The idea is that every document gradually losses its weight (or memory) as time passes according to this factor. Since F2ICM generates clusters using a document similarity measure based on the forgetting factor, newer documents have much effects on the resulting cluster structure than older ones. In this paper, we present the fundamental idea of the F2ICM method and describe its details such as the similarity measure and the clustering algorithm. Also, we show an efficient incremental statistics maintenance method of F2ICM which is indispensable for on-line dynamic environments. Keywords: clustering, on-line information processing, incremental algorithms, forgetting factors

Source Description-Based Approach for the Modeling of Spatial Information Integration Reviewed

Yoshiharu Ishikawa and Hiroyuki Kitagawa

Proceedings of the 20th International Conference on Conceptual Modeling (ER 2001) page： 41-55 2001.11

Authorship：Lead author Language：English

Rapid development of information technology such as mobile terminals and GPS systems enabled information services that provide location-oriented information based on users' positions. In this paper, we propose an approach for the modeling of information integration applications that incorporate spatial information sources in addition to conventional information sources to provide appropriate location-oriented information to users. First, we present our approach to the modeling of spatial information sources based on the source description framework. It provides a way to represent the content and the query capability of a spatial information source in a descriptive manner. Then we show a query processing scheme that finds a combination of information sources to respond to given queries and to evaluate them efficiently.

Integration of Multiple Dissemination-Based Information Sources Using Source Data Arrival Properties Reviewed

Yousuke Watanabe, Hiroyuki Kitagawa, and Yoshiharu Ishikawa

Proceedings of the 2nd International Conference on Web Information Systems Engineering (WISE 2001) page： 21-30 2001.12

Language：English

The integration of heterogeneous information sources is an important data engineering research issue. Various types of information sources are available today. They include dissemination-based information sources, which actively and autonomously deliver information from servers to users. We are developing a mediator/wrapper-based information integration system in which we employ ECA rules to define new information delivery channels, integrating multiple existing dissemination-based information sources. ECA rules in this system are derived from integration requirement specifications based on relational algebra provided by users. Dissemination-based information sources usually have data arrival properties, such as an information delivery schedule. Using the data arrival properties of underlying information sources, the system can derive more appropriate ECA rules and check the consistency of requirements more accurately. This paper proposes an extended scheme to process information integration requirements using source data arrival properties of dissemination-based information sources.

Specification of Dissemination Services and Derivation of ECA Rules in Dissemination-Based Information Integration Environments Reviewed

Tomoyuki Kajino, Hiroyuki Kitagawa, and Yoshiharu Ishikawa

IEICE Transactions on Information and Systems (Japanese Edition) Vol. J85-DI ( 1 ) page： 40-52 2002.1

Language：Japanese Publishing type：Research paper (scientific journal)

Integration of heterogeneous information sources has been one of important research in recent advanced network environments. In these days, various types of information sources are available. Dissemination-baesd information sources that actively deliver information from server sites to users are important information sources. In our research group, a dissemination-based information integration system that uses ECA rules to process dissemination-based information sources has been built to incorporate delivered information in a flexible manner. However, the users of the system have to specify and verify ECA rules by themselves. In this paper, we present a framework to specify dissemination services declaratively, and to derive ECA rules automatically.

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Papers - ISHIKAWA, Yoshiharu