• The KIPS Transactions:PartD
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• v.14D no.6
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• pp.605-614
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• 2007

As a standard query language to search XML data, XQuery and XPath were proposed by W3C. By widely using XQuery and XPath languages, recent researches focus on the development of query processing algorithm and data structure for efficiently processing XML query with the enormous XML database system. Recently, when processing XML path expressions, the concept of the structural join which may determine the structural relationship between XML elements, e.g., ancestor-descendant or parent-child, has been one of the dominant XPath processing mechanisms. However, structural joins which frequently occur in XPath query processing require high cost. In this paper, we propose a new structural join algorithm, called SISJ, based on our structured index, called SI, in order to process XPath queries efficiently. Experimental results show that our algorithm performs marginally better than previous ones. However, in the case of high recursive documents, it performed more than 30% by the pruning feature of the proposed method.

• Annual Conference of KIPS
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• 2015.04a
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• pp.57-60
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• 2015

XPath는 XML 문서를 탐색하고 필요한 부분을 추출하는데 유용한 W3C 표준 프로그래밍 언어이다. XPath를 기반으로 XSLT, XQuery와 같은 표준 언어가 정의되어 널리 사용되고 있으며, DTD, XML Schema, RelaxNG와 같은 타입 언어를 이용하여 XML 문서를 효과적으로 명세할 수 있음에도 불구하고, XPath 기반 XML 처리 프로그램을 위한 타입 검사 기법은 미비하다. 본 논문에서는 XPath 기반 프로그램을 위한 새로운 양상논리 기반의 타입 추론 기법을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.877-895
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• 2010

The state-of-the-art techniques of storing XML data, modeled as an XML tree, are node-based in the sense that they are centered around XML node labeling and the storage unit is an XML node. In this paper, we propose a generalization of such techniques so that the storage unit is an XML subtree that consists of one or more nodes. Despite several advantages with such generalization, a major problem would be inefficiency in XPath processing where the stored subtrees are to be parsed on the fly in order for the nodes inside them to be accessed. We solve this problem, proposing a technique whereby no parsing of the subtrees involved in XPath processing is needed at all unless they contain the nodes of the final query result. We prove that the correctness of XPath processing is guaranteed with our technique. Through implementation and experiments, we also show that the overhead of our technique is acceptable.

• Journal of KIISE:Databases
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• v.32 no.2
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• pp.193-203
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• 2005

XML (extensible Markup Language) is recognized as a standard of data representation and transmission on Internet. XPath is a standard for specifying parts of XML documents anda suitable language for both query processing and access control of XML. In this paper, we use the XPath expression for representing user queries and access control for XML. And we propose an access control method for XML, where we control accesses to XML documents by filtering query XPath expressions through access control XPath expressions. In the proposed method, we directly search XACT (XML Access Control Tree) for a query XPath expression and extract the access-granted parts. The XACT is our proposedstructure, where the edges are structural summary of XML elements and the nodes contain access-control information. We show the query XPath expressions are successfully filtered through the XACT by our proposed method, and also show the performance improvement by comparing the proposed method with the previous work.

• Annual Conference of KIPS
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• 2004.11a
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• pp.47-50
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• 2004

XML 은 데이터 저장과 전송을 위한 수단으로 자리잡아 가고 있으며, 관계형 DBMS를 이용해서 효과적으로 대용량의 XML 데이터의 저장과 검색에 관한 연구가 진행 되고 있다. 본 논문에서는 기 제안된 XPath Accelerator 라는 XML 데이터 인덱스 메커니즘을 상용 관계형 DBMS를 활용해서 구현하고, 이를 해당 DBMS 상에서 최대한의 성능을 위해 튜닝하는 방안을 기술한다. 이를 위해 XBench 라는 XML 전용 벤치마크 데이터를 활용해서 XPath Accelerator 의 문제점과 향후 개선 방안에 대해서도 논의한다.

• Journal of Korea Multimedia Society
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• v.15 no.9
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• pp.1133-1148
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• 2012

This paper presents a hierarchical structuring method for the multidimensional type inheritance indices (MD-TIXs) that support the processing of XML queries in XML databases. MD-TIX uses a multidimensional index structure for efficiently supporting ancestor-descendant explorations that involve both nested element and type inheritance hierarchies. However, In the case of a long Xpath, the building and maintenance of MD-TIX are very difficult because of index entry construction problem. So, we propose a type inheritance index hierarchy method for solving this difficulty. We first construct base indices that support direct relationship explorations between adjacent two types on a given Xpath, and then, based on these base indices, we construct hierarchically the derived indices that support indirect relationship explorations between any two types of Xpath until constructing one target index for supporting the full Xpath. And we also present an algorithm that efficiently constructs a partial index hierarchy for supporting given a set of sub-pathes explorations.

• Journal of KIISE:Databases
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• v.35 no.4
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• pp.307-318
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• 2008

One of the primary issues confronting XML message brokers is the difficulty associated with processing a large set of continuous XPath queries over incoming XML seams. This paper proposes a novel system designed to present an effective solution to this problem. The proposed system transforms multiple XPath queries before their run-time into a new region-based data structure, called an XP-table, by sharing their common constraints. An XP-table is matched with a stream relation (SR) transformed from a target XML stream by a SAX parser. This arrangement is intended to minimize the runtime workload of continuous query processing. Also, system performance is estimated and verified through a variety of experiments, including comparisons with previous approaches such as YFilter and LazyDFA. The proposed system is practically linear- scalable and stable for evaluating a set of XPath queries in a continuous and timely fashion.

• The KIPS Transactions:PartD
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• v.12D no.2 s.98
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• pp.189-198
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• 2005

XML is rapidly becoming the standard for data representation and exchange, and XML documents are being adopted in various applications. Since the late 1990s, some native XML database management systems(DBMSs) have been developed. More recently, commercial relational DBMS vendors try to incorporate full functionalities of XML into their products, such as Oracle, MS SQL and IBM DB2. In this paper, we implement a well-known RDBMS-based XML data storage and indexing technique, called XPath Accelerator, and tune it in an industry-leading RDBMS. Our contributions are two-folds: 1) an in-depth implementation of the XPath Accelerator technique and 2) its tuning to exploit the advanced query processing techniques of an RDBMS.

• Journal of KIISE:Databases
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• v.33 no.5
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• pp.437-452
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• 2006

In this paper, we propose an extended XPath specification which includes a special matching character '%' used in the LIKE operation of SQL in order to solve the difficulty of writing some queries to filter element contents well, using the previous XPath specification. We also present a novel technique for filtering a collection of document-centric XMLs, called Pfilter, which is able to exploit the extended XPath specification. Owing to sharing the common prefix characters of the operands in value-based predicates, the Pfilter improves the performance in processing those. We show several performance studies, comparing Pfilter with Yfilter in respect to efficiency and scalability as using multi-query processing time (MQPT), and reporting the results with respect to inserting, deleting, and processing of value-based predicates. In conclusion, our approach provides a core algorithm for evaluating the contains() function of XPath queries in previous XML filtering researches, and a foundation for building XML-based distributed information systems.

• Annual Conference of KIPS
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• 2008.11a
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• pp.348-351
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• 2008

XML 데이터 사용의 증가와 그 응용분야가 다양해짐에 따라 무선 방송 환경에서 효율적으로 XML 데이터를 전송하기 위한 기법이 요구된다. 본 논문에서는 무선으로 방송되는 XML 스트림에 대하여 복합 XPath 표현식으로 구성되는 질의를 처리하기 위한 기법을 제안한다. XML 스트림은 기존의 반구조적인 데이터의 경로요약 기법을 활용하여 생성한다. 성능평가를 통하여 제안하는 기법이 복합 XPath 표현식이 포함된 질의에 대해서도 에너지 효율적임을 보인다.