• The KIPS Transactions:PartD
• /
• v.9D no.6
• /
• pp.991-998
• /
• 2002

With the advent of XML and database languages armed with the object-oriented concept and deductive logic, the problem of efficient query processing for them has become a major issue. We describe a way of processing semi-structured XML data through an implementation of a Deductive and Object-oriented Database (DOODB) language with the explanation of query processing. We have shown how to convert an XML data model to a DOODB data model. We have then presented an efficient query processing method based on Connection Graph Resolution. We also present a knowledge-based query processing method that uses the homomorphism of objects in the database and the associative rule of substitutions.

• Journal of KIISE:Databases
• /
• v.35 no.1
• /
• pp.67-83
• /
• 2008

In order to realize ubiquitous computing, it is essential to efficiently use the resources and the computing power of mobile devices. Among others, memory efficiency, energy efficiency, and processing efficiency are required in executing the softwares embedded in mobile devices. In this paper, query processing over XML data in a mobile device where resources are limited is addressed. In a device with limited amount of memory, the techniques of XML. stream query processing need to be employed to process queries over a large volume of XML data Recently, a technique Galled XFrag was proposed whereby XML data is fragmented with the hole-filler model and streamed in fragments for processing. With XFrag, query processing is possible in the mobile device with limited memory without reconstructing the XML data out of its fragment stream. With the hole-filler model, however, memory efficiency is not high because the additional information on holes and fillers needs to be stored. In this paper, we propose a new technique called XFLab whereby XML data is fragmented with the XML labeling scheme which is for representing the structural relationship in XML data, and streamed in fragments for processing. Through implementation and experiments, XML showed that our XFLab outperformed XFrag both in memory usage and processing time.

• Journal of KIISE:Databases
• /
• v.33 no.7
• /
• pp.668-681
• /
• 2006

Due to its diverse advantages, XML has secured its position as a standard for data representation and exchange in the Internet. As a consequence, there has been much research on efficient storing and query processing of in data. Storing XML data in a relational database system warrants much benefit in data management and query processing; the system provides a strong query processing and data management function and can be applicable to XML data, its function being extended. In this paper, we design and implement a query translator that translates XQuery, a representative XML query language, into SQL:2003 query. SQL:2003, the latest SQL standard used as a substitute for SQL:1999, defines SQL/XML that supports XML. The main contribution of this paper is as follows: First, we look into the supporting features of XML, defined in the SQL:2003 standard, and propose a user-defined function for shortcoming sections. Second, we propose a way to translate XQuery into SQL that observes the latest SQL standard. Third, we describe in detail the design and the implementation of the translator to show its feasibility as a translator.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2005.05a
• /
• pp.51-54
• /
• 2005

This paper proposes an index structure which is used to process X-Path on S-XML data. There are many previous index structures based on tree structure for X-Path processing. Because of general tree index's top-down query fashion, the unnecessary node traversal makes heavy access and decreases the query processing performance. And both of the two query types for X-Path called single-path query and branching query need to be supported in proposed index structure. This method uses a combination of path summary and the node indexing. First, it manages hashing on hierarchy elements which are presented in tag in S-XML. Second, array blocks named path summary array is created in each node of hashing to store the path information. The X-Path processing finds the tag element using hashing and checks array blocks in each node to determine the path of query's result. Based on this structure, it supports both single-path query and branching path query and improves the X-Path processing performance.

• Journal of KIISE:Databases
• /
• v.32 no.2
• /
• pp.177-192
• /
• 2005

In this paper, we introduce a structural redundancy method. It reduces the query processing cost incurred when reconfiguring an XML document from divided XML data in shredding XML documents into relations. The fundamental idea is that query performance can be enhanced by analyzing query patterns and replicating data essential for the query performance. For the practical and effective structural redundancy, we analyzed three types of ID, VALUE, and SUBTREE replication. In addition, if given XML data and queries are very large and complex, it can be very difficult to search optimal redundancy set. Therefore, a heuristic search method is introduced in this paper. Finally, XML query processing cost arising by employing the structural redundancy, and the efficiency of proposed search method arc analyzed experimentally It is manifest that XML read query is performed more quick]y but XML update query is performed more slowly due to the additional update consistency cost for replicas. However, experimental results showed that in-place ID replication is useful even in having excessive update cost. It was also observed that multiple-place SUBTREE replication can enhance read query performance remarkably if only update cost is not excessive.

• Journal of KIISE:Databases
• /
• v.31 no.2
• /
• pp.183-194
• /
• 2004

As XML is a do facto standard for a data exchange language, there have been several researches on efficient processing XML queries. The most important thing to consider when processing XML queries is how efficiently we can process path expressions in queries. Some previous works make results by performing a sequence of join operations on all records corresponding to labels in the path expression. Others works check the existence of paths in the query using an RDBMS's string comparison operator and make results by extracting the records corresponding to the paths. In this paper we suggested a new query planning algorithm based on path containment relationships and two join operators supporting the planning algorithm. The join operators use only the records related to the paths in a query as input data, scan them only once, and generate result data using a pipelining mechanism. By analysis and experiments, we confirmed that our techniques(a new query planning algorithm and two join operators) achieved significantly higher performance than other previous works.

• Journal of KIISE:Databases
• /
• v.31 no.1
• /
• pp.61-71
• /
• 2004

XML can describe a wide range of data, from regular to irregular and from flat to deeply nested. Thus, XML is rapidly emerging as the do facto standard for the Web document format since XML supports an efficient data exchange and integration. Also, to retrieve the data represented by XML, several XML query languages are proposed. XML query languages such as XPath and XQuery use path expressions to traverse irregularly structured data which comprise B% elements. To evaluate path expressions, various path indexes are proposed. However, traditional path indexes are constructed by utilizing only the XML data structure. Therefore, in this paper, we propose an adaptive path index which utilizes the XML data structure as well as query workloads. To improve the query performance, the adaptive path index proposed by this paper manages the frequently used paths and the structural summary of the XML data using a hash tree and a graph structure. Experimental results show that the adaptive path index improves the query performance typically 2 to 69 times compared with the existing indexes.

• The KIPS Transactions:PartD
• /
• v.11D no.7 s.96
• /
• pp.1375-1384
• /
• 2004

Streaming data processing is an area of interest with much research under way. There has been increasing attention on the demands for efficient processing of streaming data produced in the application areas such as monitoring and sensor network. We have developed a continuous query processing system for streaming data and evaluated its performance in this paper. XML, the standard for data exchange on the web, is used as the model for the streaming data and the XQuery appended with a time interval is adopted as the query language for expressing con-tinuous queries. In the proposed system, the result is produced through background processing and materialized for reute in subsequent query processing. Through a detailed set of performance experiments, we shoed the effectiveness of the proposed system.

• Journal of KIISE:Databases
• /
• v.32 no.2
• /
• pp.204-218
• /
• 2005

XML has rapidly emerged as the standard for the interchange of data in numerous application areas. To support for efficient queries against XML data, many query languages have been designed. The query languages require the users to know the structure of the XML documents and specify search conditions on the structure. This path-based query against XML documents is a natural consequence of the hierarchical structure of XML. However, it is also desirable to allow the users to formulate no path queries against XML documents, to complement the current path-based queries. In this paper, we design a query expression capable of querying without knowledge about the structure of XML documents, and develop a query processor to evaluate no path queries.

• Journal of the Korea Society of Computer and Information
• /
• v.14 no.3
• /
• pp.1-11
• /
• 2009

XQuery query proposed by W3C is one of the standard query languages for XML data and is widely accepted by many applications. Therefore the studies for efficient Processing of XQuery query have become a topic of critical importance recently and the optimization of XQuery query is one of new issues in these studies. However, previous researches just focus on the optimization techniques for a specific XML data management system and these optimization techniques can not be used under the any XML data management systems. Also, some previous researches use predefined XML data structure information such as XML schema or DTD for the optimization. In the real situation, however applications do not all refer to the structure information for XML data. Therefore, this paper analyzes only a XQuery query and optimize by using itself of the XQuery query. In this paper, we propose 3 kinds of optimization method that considers the characteristic of XQuery query. First method removes the redundant expressions described in XQuery query second method replaces the processing order of operation and clause in XQuery query and third method rewrites the XQuery query based on FOR clause. In case of third method, we consider FOR clause because generally FOR clause generates a loop in XQuery query and the loop often rises to execution frequency of redundant operation. Through a performance evaluation, we show that the processing time for rewritten queries is less than for original queries. also each method in our XQuery query optimizer can be used separately because the each method is independent.