• Proceedings of the Korea Multimedia Society Conference
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• 2000.11a
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• pp.534-537
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• 2000

지금까지 XML문서는 사용자에게 문서내의 모든 내용을 공개하였지만, 전자상거래와 같은 특정 분야의 경우에는 사용자에 따라 문서의 일부만을 공개하는 것이 필요하다. 따라서, 사용자에게 XML 문서의 권한을 부여하고 권한에 따라 접근을 관리하는 접근 관리 시스템이 요구된다. 이를 위하여 사용자 그룹을 권한 주체의 기본 단위로, XML 문서의 엘리먼트를 권한 객체의 기본 단위로 설정하여야 한다. 그러한 권한 주체의 계층 구조는 DAG(Directed Acyclic Graph) 형태로 표현되고 문서에 대한 접근 권한은 접근 제어 리스트를 이용하여 관리된다. 그러나 권한 주체마다 모든 접근 권한을 표시해야 하기 때문에 엘리먼트 단위의 접근 관리를 위해서는 접근 제어 리스트의 크기가 커지게 되는 문제점이 발생한다. 이를 해결하기 위해서 본 논문에서는 DAG를 완전 k-ary 트리로 변환하여 접근 권한을 부모와 자식 노드간에 상속받을 수 있도록 함으로써 접근 제어 리스트의 크기를 상당히 줄이면서도 권한 주체의 접근 권한이 빨리 알아낼 수 있는 새로운 방법을 제시한다. 성능 분석 결과 새로운 방안이 기존의 전관 제어 리스트에 비해 매우 효과적임을 알 수 있다.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.4
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• pp.192-202
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• 2009

Disassembly of products at their end-of-life (EOL) is a prerequisite for recycling or remanufacturing, since most products should be disassembled before being recycled or remanufactured as secondary parts or materials. In disassembly sequence planning of EOL products, considered are the uncertainty issues, i.e., defective parts or joints in an incoming product, disassembly damage, and imprecise net profits and costs. The paper deals with the problem of determining the disassembly level and corresponding sequence, with the objective of maximizing the overall profit under uncertainties in disassembly cost and/or revenue. The solution is represented as the longest path on a directed acyclic graph where parameter (arc length) uncertainties are modeled in the form of intervals. And, a heuristic algorithm is developed to find a path with the minimum worst case regret, since the problem is NP-hard. Computational experiments are carried out to show the performance of the proposed algorithm compared with the mixed integer programming model and Conde's heuristic algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.712-714
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• 2001

매쉬 구조를 갖는 다중 프로세서에서의 오류를 허용하는 라우팅 기법은 구현에 있어 간결함을 제공하는 환경으로, 다수의 오류를 허용하기 위해 직사각형 모양의 오류 블록으로 구성하여 라우팅을 수행한다. 이 경우, 블록 내부의 정상적인 노드 역시 오류 노드로 간주되어 전체 노드의 사용율을 저하시키는데, 오류 블록을 몇 개의 확장된 매쉬로 나누고 DAG(Directed Acyclic Graph)에 적용하여 메시지 전송의 최단 거리를 구하는 RIFP(Routing for Irregular Faulty Pattern)기법으로 이를 해결하였다. 그러나, 이 기법은 노드간에 주고받는 메시지가 거치는 hop의 수가 오히려 증가되는 문제가 발생하게 된다. 본 논문에서는 증가되는 hop의 수를 억제하기 위해 목적 노드와 이웃 노드들로부터 오류블록 경계 부분까지 직선 경로를 찾는 SCP(Short-Cut Path)를 적용한 RIFP를 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.700-702
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• 2005

본 논문에서는 대규모 베이지안 망을 빠른 시간 안에 학습하기 위한 방법으로, 클러스터링을 이용한 방법을 제안한다. 제안하는 방법은 베이지안 구조 학습에 있어서 DAG(Directed Acyclic Graph)를 탐색하는 영역을 제한하기 위해 클러스터링을 사용한다. 기존의 베이지안 구조 학습 방법들이 고려하는 후보 DAG의 수가 전체 노드 수에 의해 제한되는 데 반해, 제안되는 방법에서는 미리 정해진 클러스터의 최대 크기에 의해 제한된다. 실험 결과를 통해, 제안하는 방법이 기존의 대규모 베이지안 망 학습에 활용되었던 SC(Sparse Candidate) 방법 보다 훨씬 적은 수의 후보 DAG만을 고려하였음에도 불구하고, 비슷한 정도의 정확도를 나타냄을 보인다.

• Journal of Information Processing Systems
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• v.10 no.2
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• pp.193-214
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• 2014

Load balancing is the major benefit of any distributed system. To facilitate this advantage, task duplication and migration methodologies are employed. As this paper deals with dependent tasks (DAG), we used duplication. Task duplication reduces the overall schedule length of DAG along-with load balancing. This paper proposes a new task duplication algorithm at the time of tasks assignment on various processors. With the intention of conducting proposed algorithm performance computation; simulation has been done on the Netbeans IDE. The mesh topology of a distributed system is simulated at this juncture. For task duplication, overall schedule length of DAG is the main parameter that decides the performance of a proposed duplication algorithm. After obtaining the results we compared our performance with arbitrary task assignment, CAWF and HEFT-TD algorithms. Additionally, we also compared the complexity of the proposed algorithm with the Duplication Based Bottom Up scheduling (DBUS) and Heterogeneous Earliest Finish Time with Task Duplication (HEFT-TD).

• IEMEK Journal of Embedded Systems and Applications
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• v.18 no.4
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• pp.151-157
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• 2023

RPL (IPv6 Routing Protocol for Low-power Lossy Network) is a standardized routing protocol for LLNs (Low power and Lossy Networks) by the IETF (Internet Engineering Task Force). RPL creates routes and builds a DODAG (Destination Oriented Directed Acyclic Graph) through OF (Objective Function) defining routing metrics and optimization objectives. RPL supports a leaf mode which does not allow any child nodes. In this paper, we propose INFRA-RPL which provides a dynamic leaf mode functionality to a leaf node with the mobility. The proposed protocol is implemented in the open-source IoT operating system, Contiki-NG and Cooja simulator, and its performance is evaluated. The evaluation results show that INFRA-RPL outperforms the existing protocols in the terms of PDR, latency, and control message overhead.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.5
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• pp.681-691
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• 1986

To represent the relations of the data dependency and resource conflict among micro-operations(MOP's) in the compaction process of microprograms, we propose a DDM (data dependent matrix) representation method instead of the DAG (conventional directed acyclic graph). Also, we propose a global compaction algorithm of microprograms to prevent a kind of block copying by cutting the trace at a junction block. The DDM method and compaction algoristhm have been applied to the Lah's example. The results shows that the proposed algorithm is more efficient than the conventional algorithms in reducing in reducing the total execution time and control memory space.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.6
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• pp.3046-3070
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• 2017

Nowadays, the utilization of multiprocessor environments has been increased due to the increase in time complexity of application programs and decrease in hardware costs. In such architectures during the compilation step, each program is decomposed into the smaller and maybe dependent segments so-called tasks. Precedence constraints, required execution times of the tasks, and communication costs among them are modeled using a directed acyclic graph (DAG) named task-graph. All the tasks in the task-graph must be assigned to a predefined number of processors in such a way that the precedence constraints are preserved, and the program's completion time is minimized, and this is an NP-hard problem from the time-complexity point of view. The results obtained by different approaches are dominated by two major factors; first, which order of tasks should be selected (sequence subproblem), and second, how the selected sequence should be assigned to the processors (assigning subproblem). In this paper, a hybrid proposed approach has been presented, in which two different artificial ant colonies cooperate to solve the multiprocessor task-scheduling problem; one colony to tackle the sequence subproblem, and another to cope with assigning subproblem. The utilization of background knowledge about the problem (different priority measurements of the tasks) has made the proposed approach very robust and efficient. 125 different task-graphs with various shape parameters such as size, communication-to-computation ratio and parallelism have been utilized for a comprehensive evaluation of the proposed approach, and the results show its superiority versus the other conventional methods from the performance point of view.

• Journal of KIISE
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• v.43 no.11
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• pp.1233-1244
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• 2016

In the IoT network environments for LLNs(Low power and Lossy networks), IPv6 Routing Protocol for Low Power and Lossy networks(RPL) has been proposed by IETF(Internet Engineering Task Force). The goal of RPL is to create a directed acyclic graph, without loops. As recommended by the IETF standard, RPL route recovery mechanisms in the event of a failure of a node should avoid loop, loop detection, DIO Poisoning. In this process, route recovery time and control message might be increased in the sub-tree because of the repeated route search. In this paper, we suggested RPL route recovery method to solve the routing overhead problem in the sub-tree during a loss of a link in the RPL routing protocol based on IoT wireless networks. The proposed method improved local repair process by utilizing a route that could not be selected as the preferred existing parents. This reduced the traffic control packet, especially in the disconnected node's sub tree. It also resulted in a quick recovery. Our simulation results showed that the proposed RPL local repair reduced the recovery time and the traffic of control packets of RPL. According to our experiment results, the proposed method improved the recovery performance of RPL.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.71-81
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• 2010

In grid system, Task scheduling based on list scheduling models has showed low complexity and high efficiency in fully connected processor set environment. However, earlier schemes did not consider sufficiently the communication cost among tasks and the composition process of lightpath for communication in optical gird environment. In this thesis, we propose LSOG (Leveling Selection in Optical Grid) which sets task priority after forming a hierarchical directed acyclic graph (DAG) that is optimized in optical grid environment. To determine priorities of task assignment in the same level, proposed algorithm executes the task with biggest communication cost between itself and its predecessor. Then, it considers the shortest route for communication between tasks. This process improves communication cost in scheduling process through optimizing link resource usage in optical grid environment. We compared LSOG algorithm with conventional ELSA (Extended List Scheduling Algorithm) and SCP (Scheduled Critical Path) algorithm. We could see the enhancement in overall scheduling performance through increment in CCR value and smoothing network environment.