• Title/Summary/Keyword: Caching System

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Implementation of XML Query Processing System Using the Materialized View Cache-Answerability (실체뷰 캐쉬 기법을 이용한 XML 질의 처리 시스템의 구현)

  • Moon, Chan-Ho;Park, Jung-Kee;Kang, Hyun-Chul
    • The KIPS Transactions:PartD
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    • v.11D no.2
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    • pp.293-304
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    • 2004
  • Recently, caching for the database-backed web applications has received much attention. The results of frequent queries could be cached for repeated reuse or for efficient processing of the relevant queries. Since the emergence of XML as a standard for data exchange on the web, today's web applications are to retrieve information from the remote XML sources across the network, and thus it is desirable to maintain the XML query results in the cache for the web applications. In this paper, we describe implementation of an XML query processing system that supports cache-answerability of XML queries, and evaluate its performance. XML path expression, which is one of the core features of XML query languages including XQuery, XPath, and XQL was considered as the XML query. Their result is maintained as an XML materialized view in the XML cache. The algorithms to rewrite the given XML path expression using its relevant materialized view proposed in [13] were implemented with RDBMS as XML store. The major issues of implementation are described in detail. The results of performance experiments conducted with the implemented system showed effectiveness of cache-answerability of XML queries. Comparison with previous research in terms of performance is also Provided.

A Distributed VOD Server Based on Virtual Interface Architecture and Interval Cache (버추얼 인터페이스 아키텍처 및 인터벌 캐쉬에 기반한 분산 VOD 서버)

  • Oh, Soo-Cheol;Chung, Sang-Hwa
    • Journal of KIISE:Computer Systems and Theory
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    • v.33 no.10
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    • pp.734-745
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    • 2006
  • This paper presents a PC cluster-based distributed VOD server that minimizes the load of an interconnection network by adopting the VIA communication protocol and the interval cache algorithm. Video data is distributed to the disks of the distributed VOD server and each server node receives the data through the interconnection network and sends it to clients. The load of the interconnection network increases because of the large amount of video data transferred. This paper developed a distributed VOD file system, which is based on VIA, to minimize cost using interconnection network when accessing remote disks. VIA is a user-level communication protocol removing the overhead of TCP/IP. This papers also improved the performance of the interconnection network by expanding the maximum transfer size of VIA. In addition, the interval cache reduces traffic on the interconnection network by caching, in main memory, the video data transferred from disks of remote server nodes. Experiments using the distributed VOD server of this paper showed a maximum performance improvement of 21.3% compared with a distributed VOD server without VIA and the interval cache, when used with a four-node PC cluster.

A Hashing Scheme using Round Robin in a Wireless Internet Proxy Server Cluster System (무선 인터넷 프록시 서버 클러스터 시스템에서 라운드 로빈을 이용한 해싱 기법)

  • Kwak, Huk-Eun;Chung, Kyu-Sik
    • The KIPS Transactions:PartA
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    • v.13A no.7 s.104
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    • pp.615-622
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    • 2006
  • Caching in a Wireless Internet Proxy Server Cluster Environment has an effect that minimizes the time on the request and response of Internet traffic and Web user As a way to increase the hit ratio of cache, we can use a hash function to make the same request URLs to be assigned to the same cache server. The disadvantage of the hashing scheme is that client requests cannot be well-distributed to all cache servers so that the performance of the whole system can depend on only a few busy servers. In this paper, we propose an improved load balancing scheme using hashing and Round Robin scheme that distributes client requests evenly to cache servers. In the existing hashing scheme, if a hashing value for a request URL is calculated, the server number is statically fixed at compile time while in the proposed scheme it is dynamically fixed at run time using round robin method. We implemented the proposed scheme in a Wireless Internet Proxy Server Cluster Environment and performed experiments using 16 PCs. Experimental results show the even distribution of client requests and the 52% to 112% performance improvement compared to the existing hashing method.

Utilizing Channel Bonding-based M-n and Interval Cache on a Distributed VOD Server (효율적인 분산 VOD 서버를 위한 Channel Bonding 기반 M-VIA 및 인터벌 캐쉬의 활용)

  • Chung, Sang-Hwa;Oh, Soo-Cheol;Yoon, Won-Ju;kim, Hyun-Pil;Choi, Young-In
    • The KIPS Transactions:PartA
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    • v.12A no.7 s.97
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    • pp.627-636
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    • 2005
  • This paper presents a PC cluster-based distributed video on demand (VOD) server that minimizes the load of the interconnection network by adopting channel bonding-based MVIA and the interval cache algorithm Video data is distributed to the disks of each server node of the distributed VOD server and each server node receives the data through the interconnection network and sends it to clients. The load of the interconnection network increases because of the large volume of video data transferred. We adopt two techniques to reduce the load of the interconnection network. First, an Msupporting channel bonding technique is adopted for the interconnection network. n which is a user-level communication protocol that reduces the overhead of the TCP/IP protocol in cluster systems, minimizes the time spent in communicating. We increase the bandwidth of the interconnection network using the channel bonding technique with MThe channel bonding technique expands the bandwidth by sending data concurrently through multiple network cards. Second, the interval cache reduces traffic on the interconnection network by caching the video data transferred from the remote disks in main memory Experiments using the distributed VOD server of this paper showed a maximum performance improvement of $30\%$ compared with a distributed VOD server without channel bonding-based MVIA and the interval cache, when used with a four-node PC cluster.

A Study of Educational System for Medical Technologists in Korea (한국(韓國)의 의료기사(醫療技士) 교육제도(敎育制度)에 관(關)한 조사(調査) 연구(硏究))

  • Song, Jae-Kwan;Lee, Gun-Sub;Kim, Byong-Lak;Kim, Chung-Rak;Cho, Jun-Suk;Huh, Joon;Lee, Joon-Il
    • Journal of radiological science and technology
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    • v.6 no.1
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    • pp.131-181
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    • 1983
  • After the investigation on, and the analysis of, the educational system for medical technicians and the present educational situation for medical technologies in this country, the following conclusions were drawn. 1. As of March 1983 the current academic system for education in medical technologies included the regular 4-year college courses and those of the 2-year professional junior college courses. But except in the cases on clinical pathology and physical therapy, there were no college-level departments. Particularly, no educational institutions, at whatever level, had a department for working therapies. 2. The total number of credits needed for graduation from a department of medical technologies was 150 points at a regular 4-year college and 85 to 96 points at a 2-year professional college. The obligatory minimum number of credits for a student at a professional college was set at 80 points and above. 3. As for the number of the educational institutions for medical technologies in this country, there were one regular college and 14 professional colleges, a total of 15 institutions. As many as 14 colleges had departments of clinical pathology, 12 had departments of Radiotechnology, 11 had departments of physical therapy, 12 had departments of dental technology, and eight had departments of dental hygiene. 4. The total capacity of the professional colleges in admitting new enrollment each year were 1,920 for clinical pathology, 1,552 for radiology, 1,012 for physical therapy, 1,334 for dental technologies, 828 for dental hygiene, an aggregate of 6,646 for all of the professional college departments. 5. The total number of graduates from the 12 professional colleges by department during the period of 1965-83 were 7,595 for clindical pathology, 4,768 for radiology, 2,821 for physical therapy, 3,000 for dental technologies, and 1,787 for dental hygiene, totalling 19,971 for all departments in the professional colleges. 6. In the state examination for licensed medical technicians, 12,446 have passed from among the total of 26,609 participants, representing a 45% passing ratio. By departments the ratios showed 44% for clinical pathology, 39.7% for radiology, 51.2% for physical therapy, 42.5% for dental technology, 72.5% for dental hygiene and 73.1% for working therapy. 7. As for the degree of satisfaction shown by the people in this field, 52.2 percent of the teaching staffs who responed to the questionaires said they were satisfied with their present profession, while the great majority of medical technicians(66%) replied that they were indifferent to the problem. 8. The degree of satisfaction shown by the students on their enrollment in this particular academic field was generally in the framework of indifference(43.7%), but mere students(36.5%) were satisfied with their choice than those were not satisfied(14.4%) 9. As for the student's opinions on the lectures and practicing hours, a good many students replied that, among such courses as general science and humanities courses the basic medical course, the major course and practicing hours, the hours provided for the general courses(47.1%) and practicing(47.6%) were insufficient. 10. When asked about the contents of their major courses, comparatively few students (23.6%) replied that the courses were too difficult, while a convincing majority(58.5%) said they were neither difficult nor easy. As for the appropriateness of the number of the present teaching staffs, a great majority(71.0%) of the students replied that the level of the teaching personnel in each particular field was insufficient. 11. Among the students who responded to the poll, good part of them(49.5%) wanted mandatory clinical practicing hours, and the the majority of them(64.6%) held the view that the experimental and practicing facilities of their schools were insufficient. 12. On the necessity of the attached hospitals, 71.1% of the teaching staffs and 58.0% of the medical technicians had the opinion that this kind of facility was indispensable. 13. As for the qualifications for applicants to the state examination in the licensing system for medical technicians, 52.2% of the teacher's and 36% of the medical technicians replied that the present system granting the qualifications according to the apprenticeship period should be abolished. 14. On the necessity of improving the present system for education in medical technologies, an overwhelming majority(94.4% of the :caching staffs, 92.0% of the medical technicians and 91.9% of students) of these polled replied that the present system should be changed for the better. 15. On the method of changes for the present educational system, a great majority(89.4% of the teaching staffs, 80.4% of the medical technicians and 90.1% of the students) said that the system must be changed so that it fits into the reality of the present day. 16. As for the present 2-year program for the professional colleges, 61.6% of the teachers, 72.0% of the medical technicians and 38.8% of the students expressed the hope that the academic period would be extended to four regular years, hemming a full-fledged collegelevels program. 17. On the life-long eductional system for medical technicians, there was a considerable number of people who expressed the hope that an open university system(38.9% of the teaching staffs, 36.0% of the medical technicians) and a graduate school system would be set up. 18. As for the future prospects for medical technicians as professionals, the optimists ana pessimists were almost equally divided, and 41.1% of the teaching staffs 36.0% of. the technicians and 50.5% of the students expressed an intermediate position on this issue.

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