Vol. 2, No. 2, Apr. 2006
Jin-Hyuk Yang, In-Jeong Chung
Vol. 2, No. 2, pp. 67-75, Apr. 2006
Keywords: Materialized views, Data Warehouse, and Clustering
Show / Hide AbstractIn order to acquire a precise and quick response to an analytical query, proper selection of the views to materialize in the data warehouse is crucial. In traditional view selection algorithms, all relations are considered for selection as materialized views. However, materializing all relations rather than a part results in much worse performance in terms of time and space costs. Therefore, we present an improved algorithm for selection of views to materialize using the clustering method to overcome the problem resulting from conventional view selection algorithms. In the presented algorithm, ASVMRT (Algorithm for Selection of Views to Materialize using Reduced Table), we first generate reduced tables in the data warehouse using clustering based on attribute-values density, and then we consider the combination of reduced tables as materialized views instead of a combination of the original base relations. For the justification of the proposed algorithm, we reveal the experimental results in which both time and space costs are approximately 1.8 times better than conventional algorithms.
Youn-Sik Hong, Hye-Sun Hur
Vol. 2, No. 2, pp. 76-81, Apr. 2006
Keywords: Multimedia data, downstream, PDA, TCP window size, inter-packet delay
Show / Hide AbstractA PDA is used mainly for downloading data from a stationary server such as a desktop PC in an infrastructure network based on wireless LAN. Thus, the overall performance depends heavily on the performance of such downloading with PDA. Unfortunately, for a PDA the time taken to receive data from a PC is longer than the time taken to send it by 53%. Thus, we measured and analyzed all possible factors that could cause the receiving time of a PDA to be delayed with a test bed system. There are crucial factors: the TCP window size, file access time of a PDA, and the inter-packet delay that affects the receiving time of a PDA. The window size of a PDA during the downstream is reduced dramatically to 686 bytes from 32,581 bytes. In addition, because flash memory is embedded into a PDA, writing data into the flash memory takes twice as long as reading the data from it. To alleviate these, we propose three distinct remedies: First, in order to keep the window size at a sender constant, both the size of a socket send buffer for a desktop PC and the size of a socket receive buffer for a PDA should be increased. Second, to shorten its internal file access time, the size of an application buffer implemented in an application should be doubled. Finally, the inter-packet delay of a PDA and a desktop PC at the application layer should be adjusted asymmetrically to lower the traffic bottleneck between these heterogeneous terminals.
Jung-Hee Seo, Hung-Bog Park
Vol. 2, No. 2, pp. 82-87, Apr. 2006
Keywords: digital watermark, Scalable, wavelet, Public Multimedia Network
Show / Hide AbstractIn spite of the rapid development of the public network, the variety of network-based developments currently raises numerous risks factors regarding copyright violation, the prohibition and distribution of digital media utilization, safe communication, and network security. Among these problems, multimedia data tend to increase in the distributed network environment. Hence, most image information has been transmitted in the form of digitalization. Therefore, the need for multimedia contents protection must be addressed. This paper is focused on possible solutions for multimedia contents security in the public network in order to prevent data modification by non-owners and to ensure safe communication in the distributed network environment. Accordingly, the Orthogonal Forward Wavelet Transform-based Scalable Digital Watermarking technique is proposed in this paper.
Young Ha Hwang, Sung-Kee Noh, Sang-Ha Kim
Vol. 2, No. 2, pp. 88-94, Apr. 2006
Keywords: QoS, optimal cell capacity, cell planning, wireless cellular networks
Show / Hide AbstractIn wireless cellular networks, previous researches on admission control policies and resource allocation algorithm considered the QoS (Quality of Service) in terms of CDP (Call Dropping Probability) and CBP (Call Blocking Probability). However, since the QoS was considered only within a predetermined cell capacity, the results indicated a serious overload problem of systems not guaranteeing both CDP and CBP constraints, especially in the hotspot cell. That is why a close interrelationship between CDP, CBP and cell capacity exists. Thus, it is indispensable to consider optimal cell capacity guaranteeing multiple QoS (CDP and CBP) at the time of initial cell planning for networks deployment. In this paper, we will suggest a distributed determination scheme of optimal cell capacity guaranteeing both CDP and CBP from a long-term perspective for initial cell planning. The cell-provisioning scheme is performed by using both the two-dimensional continuous-time Markov chain and an iterative method called the Gauss-Seidel method. Finally, numerical and simulation results will demonstrate that our scheme successfully determines an optimal cell capacity guaranteeing both CDP and CBP constraints for initial cell planning.
YoonJung Chung, InJung Kim, DoHoon Lee
Vol. 2, No. 2, pp. 95-100, Apr. 2006
Keywords: risk management, Asset, Threats, Vulnerability, Countermeasure
Show / Hide AbstractWhile conventional business administration-based information technology management methods are applied to the risk analysis of information systems, no security risk analysis techniques have been used in relation to information protection. In particular, given the rapid diffusion of information systems and the demand for information protection, it is vital to develop security risk analysis techniques. Therefore, this paper will suggest an ideal risk analysis process for information systems. To prove the usefulness of this security risk analysis process, this paper will show the results of managed, physical and technical security risk analysis that are derived from investigating and analyzing the conventional information protection items of an information system.
Seong-il Hahm, Seongho Cho, Han Choi, Chong-kwon Kim, Pillwoo Lee
Vol. 2, No. 2, pp. 101-106, Apr. 2006
Keywords: KGrid, Globus Toolkit, Available Bandwidth Measurement, XML Schema
Show / Hide AbstractGrid computing is an emerging technology that enables global resource sharing. In Korea, the K*Grid provides an extremely powerful research environment to both industries and academia. As part of the K*Grid project, we have constructed, together with the Korea Institute of Science and Technology Information and a number of domestic universities, a supercomputer Grid test bed which connects several types of supercomputers based on the globus toolkit. To achieve efficient networking in this Grid testbed, we propose a novel method of available bandwidth measurement, called Decoupled Capacity measurement with Initial Gap (DCIG), using packet trains. DCIG can improve the network efficiency by selecting the best path among several candidates. Simulation results show that DCIG outperforms previous work in terms of accuracy and the required measurement time. We also define a new XML schema for DCIG request/response based on the schema defined by the Global Grid Forum (GGF) Network Measurement Working Group (NM-WG).
Young Ha Hwang, Sung-Kee Noh, Sang-Ha Kim
Vol. 2, No. 2, pp. 107-113, Apr. 2006
Keywords: CAC, QoS, Fairness, Integrated service, Wireless Mobile Networks
Show / Hide AbstractIt is essential to guarantee a handoff dropping probability below a predetermined threshold for wireless mobile networks. Previous studies have proposed admission control policies for integrated voice/data traffic in wireless mobile networks. However, since QoS has been considered only in terms of CDP (Call Dropping Probability), the result has been a serious CBP (Call Blocking Probability) unfairness problem between voice and data traffic. In this paper, we suggest a new admission control policy that treats integrated voice and data traffic fairly while maintaining the CDP constraint. For underprivileged data traffic, which requires more bandwidth units than voice traffic, the packet is placed in a queue when there are no available resources in the base station, instead of being immediately rejected. Furthermore, we have adapted the biased coin method concept to adjust unfairness in terms of CBP. We analyzed the system model of a cell using both a two-dimensional continuous-time Markov chain and the Gauss-Seidel method. Numerical results demonstrate that our CAC (Call Admission Control) scheme successfully achieves CBP fairness for voice and data traffic.
Jin-Hyuk Yang, In-Jeong Chung
Vol. 2, No. 2, pp. 114-123, Apr. 2006
Keywords: Ontology, Semantic Web, OWL-S, State-chart, and UML
Show / Hide AbstractWe present in this paper the methodology for automatic generation of OWL-S service model ontology along with the results and issues. First, we extract information related to atomic services and their properties such as IOPE from the UML class diagram, and retrieve information related to the composition of services from the UML state-chart diagram. Then, the XSLT applications utilize the acquired information to generate the OWL-S service model ontology through the predefined mappings between OWL-S constructs for composite services and UML state-chart primitives. For the justification of generated service ontology, several validation checks are performed. Our service ontology generation method is general and fully automatic, as well as effective, in that it is achieved in an environment familiar to developers, and information needed to generate service ontology is provided necessarily during service development. It is also noticeable to facilitate representing the condition with GUI rather than a complex language such as OCL.
Jun-Wook Lee, Yong-Joon Lee
Vol. 2, No. 2, pp. 124-129, Apr. 2006
Keywords: spatiotemporal data mining, Spatiotemporal Knowledge Discovery, Spatiotemporal Moving Pattern, discovery framework
Show / Hide AbstractWith the explosive increase in the generation and utilization of spatiotemporal data sets, many research efforts have been focused on the efficient handling of the large volume of spatiotemporal sets. With the remarkable growth of ubiquitous computing technology, mining from the huge volume of spatiotemporal data sets is regarded as a core technology which can provide real world applications with intelligence. In this paper, we propose a 3-tier knowledge discovery framework for spatiotemporal data mining. This framework provides a foundation model not only to define the problem of spatiotemporal knowledge discovery but also to represent new knowledge and its relationships. Using the proposed knowledge discovery framework, we can easily formalize spatiotemporal data mining problems. The representation model is very useful in modeling the basic elements and the relationships between the objects in spatiotemporal data sets, information and knowledge.
A Study of a Server Selection Model for Selecting a Replicated Server based on Downstream Measurement in the Server-sideSeung-Hae Kim, Won-Hyuk Lee, Gi-Hwan Cho
Vol. 2, No. 2, pp. 130-136, Apr. 2006
Keywords: server selection, replicated server, Measurement
Show / Hide AbstractIn the distributed replicating server model, the provision of replicated services will improve the performance of the providing service and efficiency for clients. Efficiently composing the server selection algorithm decreases the retrieval time for replicated data. In this paper, we define the system model that selects and connects the replicated server that provides an optimal service using the server-side downstream measurement and propose a server selection algorithm.
Choonho Son, Jeong-Han Yun, Hyun-Goo Kang, Taisook Han
Vol. 2, No. 2, pp. 137-142, Apr. 2006
Keywords: Embedded System, Hardware Controller, Device driver, Code Generation, Co-design
Show / Hide AbstractA large portion of the embedded system development process involves the integration of hardware and software. Unfortunately, communication across the hardware/software boundary is tedious and error-prone to create. This paper presents an automatic hardware/software interface generation system. As the front-end of hardware/software co-design frameworks, a system designer defines XML specifications for hardware functions. Our system generates hardware/software interfaces including Device Driver, Driver API, and Device Controller from these specifications. Embedded software designers can easily use hardware just like system libraries. Our system reduces the mistakes and errors that can be occurred when a software programmer directly connects software to hardware, and supports balancing labors between hardware developers and software programmers. Moreover, this system can be used as the back-end for a hardware/software co-design framework.