• The KIPS Transactions:PartD
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• v.11D no.2
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• pp.317-324
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• 2004

Containment queries for XML documents is one of the most important query types, and thus the efficient support for this type of query is crucial for XML databases. Recently, object-relational database management system (ORDBMS) vendors try to store and retrieve XML data in their products. In this paper, we propose an extensible index to support containment queries over the XML data stored as BLOB type in ORDBMSs. That is, we describe how to implement the index using the extensibility feature of an ORDBMS, and describe its usage.

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

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.243-253
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• 2005

Dissemination of XML data on the internet could breach the privacy of data providers unless access to the disseminated XML data is carefully controlled. Recently, the methods using encryption have been proposed for such access control. However, in these methods, the performance of processing queries has not been addressed. A query processor cannot identify the contents of encrypted XML data unless the data are decrypted. This limitation incurs overhead of decrypting the parts of the XML data that would not contribute to the query result. In this paper, we propose the notion of query-aware decryption for efficient processing of queries against encrypted XML data. Query-aware decryption allows us to decrypt only those parts that would contribute to the query result. For this purpose, we disseminate an encrypted XML index along with the encrypted XML data. This index, when decrypted, informs us where the query results are located in the encrypted XML data, thus preventing unnecessary decryption for other parts of the data. Since the size of this index is much smaller than that of the encrypted XML data, the cost of decrypting this index is negligible compared with that for unnecessary decryption of the data itself. The experimental results show that our method improves the performance of query processing by up to 6 times compared with those of existing methods. Finally, we formally prove that dissemination of the encrypted XML index does not compromise security.

• Journal of Information Technology and Architecture
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• v.10 no.1
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• pp.123-135
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• 2013

This paper presents a two-dimensional grouping index(2DG-index) for efficient processing of XML filtering queries. Recently, many index techniques have been suggested for the efficient processing of structural relationships among the elements in the XML database such as an ancestor- descendant and a parent-child relationship. However, these index techniques focus on simple path queries, and don't consider the path queries that include a condition value for filtering. The 2DG-index is an index structure that deals with the problem of clustering index entries in the twodimensional domain space that consists of a XML path identifier domain and a filtering data value domain. For performance evaluation, we have compared our proposed 2DG-index with the conventional one dimensional index structure such as the data grouping index (DG-index) and the path grouping index (PG-index). As the result of the performance evaluations, we have verified that our proposed 2DG-index can efficiently support the query processing in XML databases according to the query types.

• Journal of KIISE:Databases
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• v.32 no.4
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• pp.416-428
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• 2005

In the paper we propose an index method for XML streaming services, where a server broadcasts XML data to a lot of clients in wireless information systems. In order to control the access and tuning time of mobile clients, the proposed method constructs the XML stream through replicating partial index intermixed with parts of data. For this purpose, we propose a two-level tree structure for separating index and XML data into two parts: replicated vs. non-replicated. We analyze the performance of the proposed method with respect to access time and tuning time. With the analysis result, we derive the optimal level value.

• Journal of KIISE:Databases
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• v.31 no.3
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• pp.320-330
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• 2004

Query languages for XML use paths in a data graph to represent queries. Actually, paths in a data graph are used as a basic constructor of an XML query. User can write more expressive Queries by using Patterns (e.g. regular expressions) for paths. There are many identical paths in a data graph because of the feature of semi-structured data. Current researches for indexing XML utilize identical paths in a data graph, but such an index can grow larger than source data graph and cannot guarantee efficient access path. In this paper we propose a partitioning technique that can partition all the paths in a data graph. We develop an index graph that can find appropriate partitions for a path query efficiently. The size of our index graph can be adjusted regardless of the source data. So, we can significantly improve the cost for index graph traversals. In the performance study, we show our index much faster than other graph based indexes.

• Journal of Korea Multimedia Society
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• v.8 no.6
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• pp.729-734
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• 2005

In order to access XML data stored in object databases, an efficient index scheme is inevitable. There have been several index schemes that can be used to efficiently retrieve XML data stored In object databases, but they are all the single path indexes that support indexing along a single schema path. Henee, if a query contains an extended path which is denoted by wild character ('*'), a query processor has to examine multiple index objects, resulting in poor performance and inconsistent index management. In this paper, we propose MPI (Multi-Path Index) scheme as a new index scheme that provides the functionality of multiple path indexes more efficiently, while it uses only one index structure. The proposed scheme is easy to manage since it considers the extended path as a logically single schema path. It is also practical since it can be implemented by little modification of the B -tree index structure.

• Journal of Korea Multimedia Society
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• v.11 no.7
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• pp.905-913
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• 2008

Many heterogeneous XML documents are being widely used with the increasing employment of XML, and the importance of data structure research for more efficient document management has been growing steadily. We propose a query processing technique which uses parent node information in a partitioned inverted index tree. The searching efficiency of these heterogeneous documents is greatly influenced by the number of query processing and the amount of target data sets in many ways. Therefore, considering these two factors is very important for designing a data structure. First, our technique stores parent node's information in an inverted index table. Then using this information, we can reduce the number of query processing by half. Also, the amount of target data sets can be lessoned by using partitioned inverted index table. Some XML documents collected from the Internet will be used to demonstrate the new method, and its high efficiency will be compared with some of the existing searching methods.

• Journal of KIISE:Databases
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• v.36 no.1
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• pp.50-62
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• 2009

In wireless and mobile environments, data broadcasting is recognized as an effective way for data dissemination due to its benefits to bandwidth efficiency, energy-efficiency, and scalability. In this paper, we address the problem of delayed query processing raised by tree-based index structures in wireless broadcast environments, which increases the access time of the mobile clients. We propose a novel distributed index structure and a clustering strategy for streaming XML data which enable energy and latency-efficient broadcast of XML data. We first define the DIX node structure to implement a fully distributed index structure which contains tag name, attributes, and text content of an element as well as its corresponding indices. By exploiting the index information in the DIX node stream, a mobile client can access the wireless stream in a shorter latency. We also suggest a method of clustering DIX nodes in the stream, which can further enhance the performance of query processing over the stream in the mobile clients. Through extensive performance experiments, we demonstrate that our approach is effective for wireless broadcasting of XML data and outperforms the previous methods.

• Journal of KIISE:Databases
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• v.30 no.4
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• pp.420-428
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• 2003

XML is a data-oriented language to represent all types of documents including web documents. By means of the advent of XML-based document generation tools and grow of proprietary XML documents using those tools and translation from legacy data to XML documents at an accelerating pace, we have been gotten a large amount of differently-structured XML documents. Therefore, it is more and more important to retrieve the right documents from the document set. But, previous works on XML have mainly focused on the storage and retrieval methods for a large XML document or XML documents had a same DTD. And, researches that supported the structural difference did not efficiently process path queries on the document set. To resolve the problem, we suggested a new inverted index mechanism using RDBMS and proved it outperformed the previous works. And especially, as it showed the higher efficiency in indirect containment relationship, we argues that the index structure is fit for the differently-structured XML document set.