• Journal of Communications and Networks
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• v.11 no.4
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• pp.337-349
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• 2009

In this paper, we introduce a novel mobility model for mobile sinks in which the sinks move towards randomly distributed destinations, where each destination is associated with a mission. The novel mobility model is termed the random mobility with destinations. There have been many studies on mobile sinks; however, they merely support two extreme cases of sink mobility. The first case features the most common and general mobility, with the sinks moving randomly, unpredictably, and inartificially. The other case takes into account mobility only along predefined or determined paths such that the sinks can gather data from sensor nodes with minimum overhead. Unfortunately, these studies for the common mobility and predefined path mobility might not suit for supporting the random mobility with destinations. In order to support random mobility with destination, we propose a new protocol, in which the source nodes send their data to the next movement path of a mobile sink. To implement the proposed protocol, we first present a mechanism for predicting the next movement path of a mobile sink based on its previous movement path. With the information about predicted movement path included in a query packet, we further present a mechanism that source nodes send energy-efficiently their data along the next movement path before arriving of the mobile sink. Last, we present mechanisms for compensating the difference between the predicted movement path and the real movement path and for relaying the delayed data after arriving of the mobile sink on the next movement path, respectively. Simulation results show that the proposed protocol achieves better performance than the existing protocols.

• The KIPS Transactions:PartD
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• v.13D no.1 s.104
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• pp.1-10
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• 2006

This paper introduces the development XPERT(XML Query Processing Engine using Relational Technologies) which is based on relational model. In our system we have used a decomposed approach to store XML files in relational tables. XML queries are translated to SQLs according to the table schema, and then they are sent to the relational DBMS to get the results back. Our translation scheme produces AST(Abstract Syntax Tree) by analyzing XQuery expressions at first. And on traversing AST proper SQLs are generated. Translated SQLs can reduce the number of joins by using path information and utilize dewey number to preserve document originated orderings among compoments in XML. In addition we propose the efficient algorithms of XPath and XQuery translation. And finally we show the implementation of our prototype system for the functional evaluations.

• Journal of KIISE:Databases
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• v.37 no.3
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• pp.137-145
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• 2010

Wireless sensors play important roles in various areas as ubiquitous computing is generalized. Depending on applications properties, each sensor can be equipped with limited computing power in addition to general function of gathering environment-related information. One of main issues in this environment is to improve energy-efficiency in sensor nodes. In this paper, we devise a new attribute-query processing algorithm. Each sensor has to maintain partial information locally about attributes values gathered at its all descendent nodes. As the volume is higher, however, the maintenance cost also increases. And the update cost also has to be considered in the proposed algorithm. Thus, some bits, AVB(Attribute-Value Bits), are delivered instead of the value itself, where each bit represents a bound of attribute. Thus, the partial information can decrease the number of exchanged messages with a little cost during query processing. Through simulation works, the proposed algorithm is analyzed from several points of view.

• 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.

• The Journal of Society for e-Business Studies
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• v.12 no.3
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• pp.211-234
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• 2007

In e-business, XML is a major format of data and it is essential to efficiently process queries against XML data. XML query caching has received much attention for query performance improvement. In employing XML query caching, some efficient technique of cache replacement is required. The previous techniques considered as a replacement unit either the whole query result or the path in the query result. The former is simple to employ but it is not efficient whereas the latter is more efficient and yet the size difference among the potential victims is large, and thus, efficiency of caching would be limited. In this paper, we propose a new technique where the element in the query result is are placement unit to overcome the limitations of the previous techniques. The proposed technique could enhance the cache efficiency to a great extent because it would not pick a victim whose size is too large to store a new cached item, the variance in the size of victims would be small, and the unused space of the cache storage would be small. A technique of XML semantic cache replacement is presented which is based on the replacement function that takes into account cache hit ratio, last access time, fetch time, size of XML semantic region, size of element in XML semantic region, etc. We implemented a prototype XML semantic cache system that employs the proposed technique, and conducted a detailed set of experiments over a LAN environment. The experimental results showed that our proposed technique outperformed the previous ones.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.434-438
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• 2008

Massive data are continuously produced with a data rate of over several terabytes every day. These applications need effective clustering algorithms to achieve an overall high performance computation. In this paper, we propose ancestor as cluster center based approach to clustering, the K-means algorithm using ancestor. We modify the K-means algorithm. We present a clustering architecture and a clustering algorithm that minimize of I/Os and show a performance with excellent. In our experimental performance evaluation, we present that our algorithm can improve the I/O speed and the query processing time.

• The KIPS Transactions:PartD
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• v.12D no.2 s.98
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• pp.259-266
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• 2005

Recently data centric routing or application dependent routing protocols are emerged in mobile ad hoc networks. In this paper, we propose a routing method for query processing in MANET(Mobile Ad hoc NETwork) environment, called road-based query routing, with consideration on real time traffic information of large number of vehicles. In particular, we focus on the method that process arrival time dependent shortest path query in MANET without a central server on the road networks. The main idea of our approach lies in a routing message that includes query predicates based on the road connectivity and on data gathering method in real time from vehicles on the road by ad-hoc network. We unify route discovery phase and data delivery(query processing) phase in our mechanism and reduce unnecessary flooding messages by pruning mobile nodes which are not on the same or neighboring road segments. In order to evaluate the performances of the proposed method, we established a model of road networks and mobile nodes which travel along the roads. The measurement factor is the number of nodes to whom route request is propagated according to each pruning strategy. Simulation result shows that road information is a dominant factor to reduce the number of messages.

• Journal of KIISE
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• v.43 no.4
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• pp.489-496
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• 2016

XML can effectively express structured or semi-structured data as well as relational databases. XQuery is a query language for retrieving information for such an XML document. In this paper, an XQuery composer is designed and implemented, with an API provided for XQuery processors, and a proper processor is registered. This composer shows query results immediately processed by the processor. As this composer contains a parser for XQuery, it can compose XQuery effectively using a diverse dialog box designed for XQuery grammar. A dialog box is affiliated with a clause region, which is a region that algebra operates from the parsing tree. It can compose path expressions for an XML document easily as it shows an element tree from DTD graphically. Path expressions are composed automatically by marking elements in the structural hierarchy and by specifying the predicate of an element partially.

• The KIPS Transactions:PartD
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• v.13D no.2 s.105
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• pp.157-164
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• 2006

Since XML is emerging as the de facto standard for exchanging and representation of data on the web, the amount of XML data has rapidly increased. Thus, the need for effective store and retrieval of U data has arisen. Since the existing techniques such as XRel which is an XML storage and management technique using RDBMS simply record the existing all label paths, diverse classes of label path expressions could not be efficiently supported. In this paper, we present a technique which supports storage and retrieval for XML data using RDBMS efficiently compared with the existing approaches. Since the proposed technique keeps the XML path index on the relational database and replace label paths with path identifiers, diverse XML queries can be evaluated compared with existing approaches. Also, the proposed technique does not require the modification of the relational database engine and consumes the disk space less. Our experimental result demonstrates the better query performance compared with existing techniques.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.430-448
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• 2001

In navigation system, a primary task is to compute the minimum cost route from the current location to the destination. One of major problems for navigation systems is that a significant amount of computation time is required when the digital road map is large. Since navigation systems are real time systems, it is critical that the path be computed while satisfying a time constraint. In this paper, we have developed a HiTi(Hierarchical MulTi) graph model for hierarchically structuring large digital road maps to speedup the minimum cost path computation. We propose a new shortest path algorithm named SPAH, which utilizes HiTi graph model of a digital road map for its computation. We prove that the shortest path computed by SPAH is the optimal. Our performance analysis of SPAH also showed that it significantly reduces the computation time over exiting methods. We present an in-depth experimental analysis of HiTi graph method by comparing it with other similar works.