• Journal of KIISE:Computing Practices and Letters
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• v.9 no.2
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• pp.109-122
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• 2003

As XML documents become popular in the World Wide Web, a lot of research is being done on XML storage systems that store and manage XML documents using existing DBMSS. However, most of them have been done in the context of relational DBMSS rather than object-relational DBMSS, which have more powerful modeling capability than relational ones. In this paper, we design and implement an XML storage system, ODYSSEUS/XMLStore, for the ODYSSEUS object-relational DBMS that has been under development at KAIST. First, we analyze the mapping from the structure of XML documents to the relational or object-relational database schema. Second, we propose a method for describing the mapping analyzed using a standard language, XML Schema. Third, we propose a storage structure for storing the mapping information specified by the users in the database. Fourth, we propose detailed algorithms for storing XML documents in the relational or object-relational database based on the mapping information provided by the users.

• The Transactions of the Korea Information Processing Society
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• v.7 no.7
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• pp.1997-2007
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• 2000

This paper presents a new benchmark for object-relational database systems, which are regarded as the next-generation database system. This benchmark has been developed to evaluate system performance peculiar to object-relational database systems. The design philosophy, test databases, an test queries of the benchmark are presented. This benchmark features scaleability, use of a synthesized database only, and a query-oriented evaluation. We have implemented his benchmark with two commerical object-relational database systems and the experimental results are also reported.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.9-17
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• 2005

XML is rapidly spreading as a standard for data representation and exchange, and XML documents are adopted in various applications. According to this trend, researches in database has also focused on efficient storage and retrieval of XML documents. Recently, major (object) relational DBMS vendors support XML functionality, and several native XML DBMSs have been developed in academic or industry side. In addition, various benchmarks have been proposed so as to evaluate these na database performance. In this paper, we evaluate the XBench benchmark using a commercial object-relational DBMS, analyze its performance, and investigate the future improvements of object-relational DBMSs for XML support.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2007.02a
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• pp.163-167
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• 2007

We propose an XML document storage system, called XDMS (XML Document Management System), by using an object-relational DBMS. XDMS generates object database schema from XML Schema and stores the XML documents in an object-relational database. SAX parser is used for understanding the structure of the XML documents, and XDMS transforms the documents into objects in the database. Experiment shows that object-relational databases provide more efficient storage and query model compared with relational databases.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.179-182
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• 1996

Database management systems are now used in almost every organization to maintain and utilize important collections of information. Relational DBMSs have a firm theoretical base. However, it lacks important features needed for representing certain critical aspects of an entity. One alternatives to remedy this problem is to adopt the object-oriented approach to the data model development process. In this paper, we tried to show the advantages of object-oriented data model design process for the development of extended relational database schema needed for the integrated plant information system at H. Heavy Industry Co.

• Journal of KIISE:Databases
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• v.31 no.4
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• pp.432-443
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• 2004

As the XML data has been widely used in the Internet, it is necessary to store and retrieve the XML data by using DBMSs. However, relational DBMSs suffer from the model difference between graph structure of the XML data and table forms in relational databases. We propose an ORDBMS-based DTD-dependent XML data management system Xing. Xing stores XML data in a DTD-dependent form in an object database. Since the object database schema has a graph structure and supports multi-valued attributes, mapping from an XML data model and queries into an object data model and OQLs is a simple problem. For rapid storing of large quantities of the XML data, we use SAX parser with customized Xing-tree which requires a small memory space compared with the DOM-tree. Xing also returns the query result in an XML document form. We have implemented the Xing system on top of UniSQL object-relational DBMS for the validity checking and performance comparison. For XML genome data from GenBank, and experimental evaluation shows that Xing can provide significant performance improvement (maximum 10 times) compared with the relational approach.

• Journal of Information Technology Applications and Management
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• v.12 no.2
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• pp.29-43
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• 2005

The paper presents the EBORD (Extended Benchmark for Object-Relational Databases) benchmark, which is an extension of the BORD benchmark for object-relational databases. The EBORD benchmark is developed to evaluate the database common functions that should be supported in modern database systems. Besides the 36 test queries already defined in the BORD benchmark, totally 22 test queries in five categories are newly defined in order to measure the index-relevant performance issues and database import capabilities. The EBORD benchmark also features scalability, use of a synthesized database, and a query-oriented evaluation. In order to show the feasibility of the proposed benchmark, we implement it with two commercial database systems. The experimental results and analyses are also reported.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.468-483
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• 2001

In order to enhance the performance, cursor stability, which is a variant of isolation lvel 2 in relational DBMSs, has been widely used in place of isolation level 3, which uses strict two phase locking. However, cursor stability is much less usable in object-relational DBMSs (ORDBMSs) because navigational applications in ORDBMSs can suffer from critical inconsistency problems such as dangling pointers, lost updates, and reading inconsistent complex objects. In this paper, we propose a new isolation level, navigation stability, that prevents the inconsistency problems of cursor stability for navigational applications, while avoiding significant degradation of the concurrency of level 3. First, we analyze the inconsistency problems of cursor stability for navigational applications. Second, we define navigation stability as an extension of cursor stability and show that it solves those inconsistency problems of cursor stability in ORDBMSs. For workloads consisting of transactions of long duration, compared with level 3, the throughput of navigation stability is enhanced by up to 200%; the average response time reduced by as much as 55%; and the abort ratio reduced by as much as 77%. From these results, we conclude that navigation stability is a useful isolation level in ORDBMSs that can be used in place of isolation level 3 to improve the performance and concurrency without significantly sacrificing consistency.

• Journal of KIISE:Databases
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• v.27 no.4
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• pp.549-561
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• 2000

In database management systems(DBMSs), partial rollback is a useful facility that cancels part of the executed operations upon user's requests without a total rollback. Many relational DBMSs(RDBMSs) provide this facility, However, object-orientccd DBMSs (OODBMSs) cannot utilize the previous recovery scl18lne of partial rollback usccd in (RDBMSs) since, unlike RDBMSs, they use a dual buffer consisting of an object buffer and a page buffer. Therefore, a new recovery scheme is required that rolls back the data efficiently in the dual buffer. We propose four partial rollback schemes in OODBMSs that use a dual buffer. We classify the proposed schemes into the single buffer based partial rollback scheme and the dual buffer based partial rollback scheme according to the number of buffers used for partial rollback processing. We further classify them into Uthe page buffer based partial rollback scheme, 2)the object buffccr based partial rollback scheme, 3)the dual buffer based partial rollback scheme using soft log, and 4)the dual buffer based partial rollback scheme using shadows. We evaluate the performance by mathematical analysis and experiments. The results show that the dual buffer based partial rollback scheme using shadows provides the best performance.

• Journal of KIISE:Databases
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• v.30 no.2
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• pp.109-124
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• 2003

Although most commercial relational DBMSs Provide a graphical query language for the user friendly interfaces of the databases, few research has been done for graphical query languages in object databases. Expressing complex query conditions in a concise and intuitive way has been an important issue in the design of graphical query languages. Since the object data model and object query languages are more complex than those of the relational ones, the graphical object query language should have a concise and intuitive representation method. We propose a graphical object query language called GOQL (Graphical Object Query Language) for object databases. By employing simple graphical notations, advanced features of the object queries such as path expressions including set attributes, quantifiers, and/or methods can be represented in a simple graphical notation. GOQL has an excellent expressive power compared with previous graphical object query languages. We show that path expressions in XSQL(1,2) can be represented by the simple graphical notations in GOQL. We also propose an algorithm that translates a graphical query in GOQL into the textual object query with the same semantics. We finally describe implementation results of GOQL in the Internet environments.