Kyung-Lang Park

Personalized Service Discovery in Ubiquitous Computing Environments

In ubiquitous computing environments, users want to discover the most appropriate service to support their tasks. Because the most appropriate service depends on user preferences and context, service discovery protocols should personalize results. A service discovery framework based on the virtual personal space (VPS)-that is, a virtual administrative domain of services managed for the user-aims to provide this personalization. In this framework, personal operating middleware embedded in a personal device manages a set of contextually close services in the users VPS. An inference module supports this management. Laboratory evaluations show that the VPS framework helps users find high-quality, appropriate services.

An efficient method to create business level events using complex event processing based on RFID standards

RFID systems should be designed to process a large number of RFID data in real time. Therefore, there have been much research and company studies regarding RFID data processing. One of methods is CEP (Complex Event Processing), which can provide a method to process RFID data efficiently. However, previous work is just focused on raw RFID data processing, such as data filtering, the elimination of duplicated data, and the aggregation of data. Also, it creates primitive events based on just one physical or logical reader. Therefore, processing overhead for complex events may increase. And it cannot provide business level events. Therefore, we propose a method that can reduce processing overhead and create business level events by using CEP. Proposed method provides two primitive events that are defined by using the relationship of two readers. Thus, when any pattern of events is matched for a specific complex event, business level events can be generated and execution time can be reduced comparing with other mechanisms without those events. And, execution time can be reduced by about 57% as compared to others.

An efficient collective communication method for grid scale networks

This research is to design a collection of effective collective operations for the Grid scale network environment. In the Grid, several network features should be specified and adapted into the algorithmic design of collective operations. For this, we characterize the Grid and design hierarchical latency optimal tree algorithm for the MPI (message passing interface) library. The experimental results show that performance gain in performing collective operations can be achieved by around 160% compared with MPICH-G2 which is based on the flat algorithm.

Dynamic Topology Selection for High Performance MPI in the Grid Environments

MPI (Message Passing Interface) is getting more popular and important even in the Grid, but its performance still remains a problem, which is caused by the communication bottleneck on wide area links. To overcome such performance wall problem, we propose a dynamic topology selection which provides an effective resource selection service based on the principles of wide area message passing. It attempts to match the communication pattern of application with the topology of resources. Consequently, the proposed method provides an optimized set of resources and improves overall application performance by reducing the communication delay. To demonstrate the proposed method, we executed parallel benchmark programs and measured each execution time in five geometrically distributed clusters by changing resource selection method. When using topology selection method, experimental results show that performance gain can be achieved by up to 200%.

VPW: An Effective Personal Space Model for Providing Ubiquitous

User-centrism is one of the most important things in ubiquitous computing. Previously, lots of researches have addressed issues for ubiquitous computing, but most of them oversimplified a personal space as a set of devices in a fixed location or in a communication-ranged space. Thus, they have had a problem to describe sophisticated user-centric services. In this paper, we propose an effective personal space model called VPW (virtual personal world) for providing ubiquitous services. VPW includes various objects over several locations, tasks in progress, and proxies of other users. Thus, service provision based on VPW supports more delicate user-centric adaptation, use of multiple devices spread over locations, and harmony between multiple users and multiple services. Eventually, it increases user satisfaction in providing ubiquitous services. Experimental results show the VPW-based approach increase user satisfaction by around 20% compared to the location-based approach and by around 15% compared to the range-based approach

A programmable context interface to build a context infrastructure for worldwide smart applications

Context-awareness is one of the most important technologies for the ubiquitous computing. To embed such a technology into applications, first of all, a well-defined architectural framework is required to support applications to obtain necessary contexts. Several studies have been proposed, but most of them overlooked one fundamental feature that contexts are subjective things and context-awareness is subjective behavior. Thus, providing pre-defined, pre-programmed operators which generate contexts by combining a couple of sensed data is very impractical. Instead, in this paper, we provide a well-defined programmable interface to applications, so that they can obtain and use contexts according to their own ideas. To evaluate our architecture and context interface, we implement all components comprising of the context infrastructure and perform several experiments. The results show the proposed method provides a flexible and expressive interface, but does not countervail the performance.

Design and Implementation of a Dynamic Communication MPI Library for the Grid

Abstract The authors design and implement a dynamic and effective communication MPI (Message-Passing Interface) library for the grid environment, especially to design collective operations such as broadcast and reduce. The purpose of the grid environment is to aggregate a large number of resources. So, it is inevitable that networks will be heterogeneous, and thus application performance will be affected. However, these issues have not until now been considered in designing communication primitives. Thus, these characteristics from the grid networks are specified and adapted into the communication algorithm design in this research. For an effective solution, we characterize the grid network on the basis of actual measurement, and design an effective communication algorithm called HLOT (Hierarchical Latency Optimal Tree) that can reduce the communication delay by utilizing the network status aggressively. Also, by using the proposed algorithm, we implement various collective communication routines of MPI library and demonstrate their effectiveness. The experimental results show that performance gain of more than 200% can be achieved in performing collective operations and around 130% in performing an applications benchmark, compared to MPICH-G2, that is, conventional grid-enabled MPI library.

A personalized and scalable service broker for the global computing environment

Service broker is a software component that maps user’s request to proper services. By using the broker, users can access various services without any knowledge of the services. However, design of the service broker for GCE (Global Computing Environment) is quite difficult because a broker cannot cope with all the information of services which are spread over the world. Thus, we need to build new architectural foundations for global service brokering. In this paper, we propose a scalable broker system for GCE based on the federation of personalized brokers. In our broker system, every user can have a service broker. The broker maintains the information of services related to the user and exchanges the information with neighboring brokers if necessary. As a result, the broker can provide proper services to users faster and a burden of brokers can also be decreased. Experimental results show that the proposed service broker can reduce the average service discovery time and the average operation overhead of each broker comparing to other brokering architectures.

An Efficient Management Algorithm for Gateway Readers in the Warehouse

In this paper, we propose a method that manages gateway readers in the warehouse efficiently. The basic role of gateway readers is to identify products coming in and out. Therefore, an efficient management method of gateway readers is required to improve the speed of tag identification process and reduce the number of used readers. Our proposed management method for gateway readers is based on the reuse of gateway readers. Therefore, when both products coming in and out will pass through this single gateway installed with some RFID readers, the readers can distinguish whether they are coming in or out. We examine the performance of proposed management method for gateway readers by using GEN2 simulator. As a result, we can reduce the number of readers about 62.5%, compared with the ones without any reuse.

A Smart Agent-Based Grid Computing Platform

Most of Grid computing platforms are usually configured with high performance computing servers, supercomputers, and cluster systems. The research is about to design an aggressive Grid computing platform by utilizing a large number of pervasive PCs as a Grid component. For this goal, an effective configuration method to construct a group of PCs is required as a single Grid component to be used in the same way as those cluster systems are designed and utilized as the same system technology. The configuration method is designed as a layered service architecture, i.e., physical information service, mobile management service, and point-based scheduling service, based on agent technology. The physical information service is to gather and maintain the status information of physical nodes, the mobile management service to guarantee the effective resource management by using the mobile agent, and the point-based scheduling service to provide a simple scheduling policy for the PC-based computing resource. Through this configuration method, the efficiency of the resource management and system throughput are expected to be increased. The experimental result shows that the system using this configuration method can support more than 90% of the expected performance given by a chosen set of running PC resources in general computing environment.