• Journal of KIISE:Databases
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• v.33 no.4
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• pp.423-436
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• 2006

In recent years, publish-subscribe (pub-sub) systems based on XML document filtering have received much attention. In a typical pub-sub system, subscribing users specify their interest in profiles expressed in the XPath language, and each new content is matched against the user profiles so that the content is delivered only to the interested subscribers. As the number of subscribed users and their profiles can grow very large, the scalability of the system is critical to the success of pub-sub services. In this paper, we propose a novel scalable filtering system called FiST(Filtering by Sequencing Twigs) that transforms twig patterns expressed in XPath and XML documents into sequences using Prufer's method. As a consequence, instead of matching linear paths of twig patterns individually and merging the matches during post-processing, FiST performs holistic matching of twig patterns with incoming documents. FiST organizes the sequences into a dynamic hash based index for efficient filtering. We demonstrate that our holistic matching approach yields lower filtering cost and good scalability under various situations.

• Journal of Internet Computing and Services
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• v.18 no.6
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• pp.47-53
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• 2017

Recently, huge datasets have been generating rapidly in a variety of fields. Then, there is an urgent need for technologies that will allow efficient and effective processing of huge datasets. Therefore the problems of partitioning a huge dataset effectively and alleviating the processing overhead of the partitioned data efficiently have been a critical factor for scalability and performance in distributed database system. In our work we utilized multicore servers to provide scalable service to our distributed system. The partitioning of database over multicore servers have emerged from a need for new architectural design of distributed database system from scalability and performance concerns in today's data deluge. The system allows uniform access through a web service interface to concurrently distributed databases over multicore servers, using SQMD (Single Query Multiple Database) mechanism based on publish/subscribe paradigm. We will present performance results with the distributed database system built on multicore server, which is time intensive with traditional architectures. We will also discuss future works.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.637-638
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• 2017

The MQTT broker has problems such as packet loss and delay due to degraded network performance according to traffic. However, the MQTT broker does not support a separate interface for traffic measurement, so it can not cope with network degradation. In this paper, we propose a system for traffic measurement of MQTT broker. The proposed system uses the jnetpcap library to measure all traffic to and from the MQTT broker.

• Journal of Information Technology and Architecture
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• v.10 no.2
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• pp.159-167
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• 2013

Web Services offer many benefits over other types of middleware in distributed computing. However, usage of Web Services results in large network bandwidth since Web Services use XML-based protocol which is heavier than binary protocols. Even though there have been many researches to minimize the network traffic and bandwidth usages of Web Services messages, none of them are solving problem clearly yet. In this paper, we propose a transparent proxy with cache to avoid transfer of repeated SOAP data, sent by Web Service to an application. To maintain the cache consistency, we introduce publish/subscribe paradigm using WS-Eventing between the proxy and Web Service. The implemented system based on our proposed architecture will not compromise the standards of Web Service. The evaluation of our system shows that caching SOAP messages not only reduces the network traffic but also decreases the request delays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.12
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• pp.1134-1149
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• 2013

Pub/sub system enables data users to access any necessary data without knowledge of the data producer and synchronization with the data producer. It is widely used as the middleware technology for the data-centric services. DDS (Data Distribution Service) is a standard middleware supported by the OMG (Object Management Group), one of global standardization organizations. It is considered quite useful as a standard middleware for US military services. However, it is well-known that it takes considerably long time in searching the Participants and Endpoints in the system, especially when the system is booting up. In this paper, we propose a discovery scheme to reduce the latency when the participants and Endpoints are densely distributed in a small area. We propose to modify the standard DDS discovery process in three folds. First, we integrate the Endpoint discovery process with the Participant discovery process. Second, we reduce the number of connections per participant during the discovery process by adopting the concept of successors in Distributed Hashing scheme. Third, instead of UDP, the participants are connected through TCP to exploit the reliable delivery feature of TCP. We evaluated the performance of our scheme by comparing with the standard DDS discovery process. The evaluation results show that our scheme achieves quite lower discovery latency in case that the Participants and the Endpoints are densely distributed in a local network.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.239-240
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• 2008

Korea Electric Power Research Institute has being carried out an IEC 61580 communication service test on IED trial products developed related to power IT project, "Development of Prototype for Advanced Substation Automation System based on the Digital Control Technology". This paper describes GOOSE testing, one of the IEC 61850 conformance testing items, which consists of 14 publish and subscribe test cases.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.296-309
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• 2012

In existing middleware for body sensor networks, energy limitations, hardware heterogeneity, increases in node temperature, and the absence of software reusability are major problems. In this paper, we propose an event-based grid middleware component that solves these problems using distributed resources in in vivo sensor nodes. In our multi-hop communication, we use a lightweight rendezvous routing algorithm in a publish/subscribe system of event-based communication. To facilitate software reuse and application development, a modified open services gateway initiative has been implemented in our middleware architecture. We evaluated our grid middleware in a cancer treatment scenario with combined hyperthermia, chemotherapy, and radiotherapy procedures, using in vivo sensors.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.345-348
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• 2015

스마트폰이 생활의 필수품으로 자리잡아감에 따라 인간 편의를 위해 스마트폰을 기본수단으로 많은 서비스가 제공되고 있다. 또한, 모바일 기반 서비스의 고도화로 스마트폰에 부착된 센서와 네트워크 통신을 적극적으로 활용하는 애플리케이션의 수가 증가하고 있다. 이로 인해 배터리 사용시간 단축, 통신량 증가 등 하드웨어 리소스의 부하 증대에 대한 사용자의 불만이 꾸준히 제기되고 있다. 본 논문에서는 최근 대학에서 도입하고 있는 비콘 기반 출석관리 환경에서 이러한 문제를 해결하기 위해 MQTT 프로토콜 기반 통신을 적용한 시스템을 제안하고 설계한다. 제안하는 출석관리 시스템에서는 발간/구독 방식의 경량 프로토콜인 MQTT를 사용함으로써 네트워크 부하 및 배터리 낭비를 최소화 하고자 한다.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1369-1378
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• 2017

Pub/Sub (Publish/Subscribe) paradigm is a simple and easy to use model for interconnecting applications in a distributed environment. In general, subscribers register their interests in a topic or a pattern of events and then asynchronously receive events matching their interest, regardless of the events' publisher. In order to build a low latency lightweight pub/sub system for Internet of Things (IoT) services, we propose a GQSFPS (Group Quorum System-based Fog Pub/Sub) system that is a core component in the event-driven service oriented architecture framework for IoT services. The GQSFPS organizes multiple installed pub/sub brokers in the fog servers into a group quorum based P2P (peer-to-peer) topology for the efficient searching and the low latency accessing of events. Therefore, the events of IoT are cached on the basis of group quorum, and the delay-sensitive IoT applications of edge devices can effectively access the cached events from group quorum fog servers in low latency. The performance of the proposed GQSFPS is evaluated through an analytical model, and is compared to the GQPS (grid quorum-based pud/sub system).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.12
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• pp.1179-1185
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• 2013

Trend of next generation satellite communication network is distribution and enlargement of network structure with increased network terminals, and traffic which use satellite communication is increasing and frequently occurring. Under specific satellite communication environment that various communication device dynamically forms a network domain and frequently exchanges the data, data-centric publish/subscribe data exchange is more suitable than server/client data exchange. So, this paper analyze DDS performance for application of DDS standard to distribution network management system which aims to efficiently manage limited satellite resource, and also this paper covers comparative study on DDS and SNMP(server/client data exchange). Study compares DDS and SNMP using OPNET, and result of study is analyzed from a network layer performance perspective.