• Journal of KIISE:Databases
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• v.34 no.3
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• pp.217-231
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• 2007

Frequent disconnection is connected directly to client's cache consistency problem in Mobile Computing environment. For solving cache consistency problem, research about Invalidation Report is studied. But, existent invalidation report structure comes with increase of size of invalidation report structure and decline of cache efficiency if quantity of data become much, or quantity of updated data increases. Also, while existent method confirms whole cache, invalidation report doesn't support selective listening. This paper proposes TTCI(Timestamp Tree-based Cache Invalidation scheme) as invalidation report structure that solve problem of these existing schemes and improve efficiency. We can make TTCI using timestamp of updated data, composing timestamp tree and list ID of data in updated order. If we utilize this, each client can confirm correct information in point that become own disconnecting and increase cache utilization ratio. Also, we can pare down client's resources consumption by selective listening using tree structure. We experimented in comparison with DRCI(Dual-Report Cache Invalidation) that is existent techniques to verify such efficiency of TTCI scheme.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.325-334
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• 2003

In stateless server, if an asynchronous cache invalidation scheme attempts to support local processing of read-only transaction in mobile client/sever database systems, a critical problem may occur ; the asynchronous invalidation reports provide no guarantees of waiting time for mobile transactions requesting commit. To solve this problem, the server in our algorithm broadcasts two kind of messages, asynchronous invalidation report to reduce transaction latency and periodic guide message to avoid the uncertainty of waiting time for the next invalidation report. The asynchronous invalidation report has its own sequence number and the periodic guide message has the sequence number of the most recently broadcast asynchronous invalidation report. A mobile client checks its cache validity by using the sequence numbers of these messages.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.606-628
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• 2003

Recently, there have been many research efforts reported in the literature that focus on the cache consistency problems of mobile clients resulting from their frequent disconnections with a server in mobile environments. To cope with this problem, a number of methods based on the invalidation report scheme has been proposed. However, these proposed methods are sensitive to the disconnection time of mobile clients and independent of the frequency of data updates in the server. As a result, although the number of data updated in the server is small, the traditional methods can not guarantee the cache consistency of mobile clients if their disconnection time is over the time period the invalidation report is allowed to cover. In this paper, we propose an efficient cache consistency method called CCI(Cost-based Cache Invalidation) for mobile clients that take into account not only the disconnection time but also the frequencies of data updates in the server We also present an in-depth experimental analysis by comparing CCI method with BT(Broadcasting Time stamp) method based on Invalidation Report.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.315-325
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• 2005

In mobile computing environments, a mobile host caches the data items to use the bandwidth efficiently and improve the response time of transactions. If the data items cached in mobile host are updated in the server, the server broadcasts an invalidation report for maintaining the cache consistency of mobile hosts. However, this method has a problem that the response time of mobile transactions can be long since their commit decision is delayed until receiving the invalidation report from the server In this paper, we propose the USR-MT method for improving the response time of mobile transactions. As the UGR-MT method can make a commit decision by using the data group information before receiving the invalidation report, the response time of mobile transactions can be improved. Also our method can improve the cache's efficiency since it prevents all the contents of a cache from being invalidated in the case that the disconnection of a mobile host is longer than the broadcast period of invalidation report.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.55-57
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• 2004

이동 컴퓨팅(Mo띠le Computing) 환경에서 빈번한 접속 단절은 클라이언트의 캐시 일관성(Consistency) 문제로 직결된다. 본 논문에서는 이를 해결하기 일한 무효화 보고(Invalidation Report. In)중 하나를 제시한다. 기존의 IR방식은 대량의 데이터와 빈번한 데이터의 갱신(Update)시 IR 길이의 증기폭이 상당히 크다. 이는 타임스탬프가 IR에서 차지하는 비중이 큼으로써 오는 현상이다. 또한 기존방식은 캐시 레벨의 선택적 청취(Selective tuning)를 지원하지 못하는 문제점을 가지오 있다. 이러한 점을 극복하고자 B＋Tree를 기반으로 시간 값을 구성하고 이에 따른 데이터 아이디를 재구성하는 IR방식을 제안한다. 이를 활용하면 각 클라이언트가 자신의 단절(Disconnect)된 시간에 맞는 갱신 정보를 확인할 수 있게 된다. 이러한 방법은 기존 IR의 단점을 보완하며 선택적 청취론 유도할 수 있는 효과적인 방법이다.

• Journal of the Korea Society of Computer and Information
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• v.17 no.5
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• pp.41-48
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• 2012

A Vehicular Ad-hoc Network (VANET) is a vehicular specific type of a mobile ad-hoc network, to provide temporary communications among nearby vehicles. Mobile node of VANET consumes energy and resource with participating in the member of network. In a VANET, data replication and cooperative caching have been used as promising solutions to improve system performance. Existing cooperative caching scheme in a VANET mostly focuses on weak consistency is not always satisfactory. In this paper, we propose an efficient cache management scheme to maintain strong data consistency in a VANET. We make an adaptive scheduling scheme to broadcast Invalidation Report (IR) in order to reduce query delay and communication overhead to maintain strong data consistency. The simulation result shows that our proposed method has a strength in terms of query delay and communication overhead.

• The KIPS Transactions:PartD
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• v.12D no.1 s.97
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• pp.21-30
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• 2005

In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time. A server periodically broadcasts the update data for maintaining the cache consistency of a mobile host. However, a method for maintaining cache consistency using periodic invalidation report has a problem that defers the commit decision of a mobile transaction to guarantee its serializable execution. In this paper, we propose CCM-AD method that guarantees the serializable execution of a mobile transaction even in the case that it is executed using cached data. As CCM-AD method guarantees the serializable execution of mobile transactions by using the intersection between the data broadcast to mobile host and the data updated at server. Then the CCM-AD method can reduce the delay of commitment decision of a mobile transaction. Also our method can reduce the size of invalidation report.

• Journal of Korea Technology Innovation Society
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• v.20 no.1
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• pp.127-152
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• 2017

China's utility model as a supplement to the invention patent, has short application duration, fast authorized speed, and has the same exclusive rights with patents, so companies can quickly dominate the market. But the utility model does not need to carry out substantive examination, so has lower stability, high frequency of invalid to accepted, so compare with the invention patent, difficult to be protected. In order to actively encourage the small and medium-sized enterprises to promote their inventions, and protect domestic patents, China established a protection policy of patent evaluation report for the utility model rights, especially the patent evaluation report can be used as evidence in a patent infringement trial, to provide judicial remedies for utility model patentee and the party of patent disputes. Many experts believe that the establishment of patent evaluation report system can improve the stability of the utility model patent right, and when the defendant request for invalidation of the patent right in the defense period, if there is no novelty, creativity lost or no other reason has not led to the stability of patent right given in a patent evaluation report of the utility model patents, the court may not suspend the trial, without having to wait for the Patent Reexamination Board makes the patent invalid declaration decisions, can improve the efficiency of the judicial process, accelerate the patentee's time. However, in practical patent infringement, the patent evaluation report system and invalidation system are in conflict. In this paper, through the analysis of the current China utility model system and compared with the South Korean utility model system, review the role and character of the patent evaluation report system, and through the actual cases of the utility model patent infringement litigation, analysis possible variates from the decision of patent evaluation report, to find out the reason of the patent evaluation report system being in conflict with the invalidation system, and research on the effectiveness for protecting Utility Model with China's Patent Evaluation Report.

• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.221-232
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• 2001

Due to rapid advance of wireless communication technology, demand on data services in mobile environment is gradually increasing. Caching at a mobile client could reduce bandwidth consumption and query response time, and yet a mobile client must maintain cache consistency. It could be efficient for the server to broadcast a periodic cache invalidation report for cache consistency in a cell. In case that long period of disconnection prevents a mobile client from checking validity of its cache based solely on the invalidation report received, the mobile client could request the server to check cache validity. In doing so, some schemes may be more efficient than others depending on the number of available channels and the mobile clients involved. In this paper, we propose new cache consistency schemes, effects, efficient especially (1) when channel capacity is enough to deal with the mobile clients involved or (2) when that is not the case, and evaluate their performance.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.276-284
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• 2005

In the mobile computing environment, caching data at the client's side is a useful technique for improving the performance. For caching to be effective, the cache contents must be consistent with those stored in the server. That is, unfortunately, difficult to enforce due to the frequent disconnection and mobility of clients. In the literature, the basic approach adopted is for the sever to periodically broadcast invalidation reports(IRs) that contain information about objects that have been updated recently. However IR-based cache maintenance scheme has a main drawback. Any client who has been disconnected longer than w seconds has to discard all cached items even some of them may still be valid. In this paper, we propose two main schemes which can adapt clients' losing IR messages by long disconnection. First, the client sends its disconnection time when connection is re-established, and the server uses this information to decide the size of broadcast window w dynamically. Second, the server maintains IR messages for a given period of time and a client who has been disconnected longer than w seconds can verify its cache consistency individually. Compared to previous IR-based schemes, our schemes can significantly reduce cache missing and uplink request and improve the throughput by reducing response time.