O surgimento de novos serviços e aplicações baseados na Web tem provocado um aumento desenfreado na quantidade de usuários da World Wide Web que, por sua vez, se torna cada vez mais popular no mundo dos negócios. Sites de e-commerce, que demandam grande tráfego de requisições, têm adotado sistemas de servidores Web distribuídos, como a arquitetura Web Cluster. Isso se deve ao fato de enfrentarem frequentemente situações de sobrecarga, durante as quais podem deixar de atender requisições de transação (com grande probabilidade de gerar renda) por conta do aumento na demanda de requisições de navegação (geram renda apenas de forma indireta). A utilização ineficiente de recursos pode comprometer o desempenho do sistema e é nesse contexto que este trabalho se insere. Neste trabalho foi desenvolvido um modelo de Servidor Web para E-Commerce (SWE-C),validado por meio de um modelo de simulação e uma carga sintética gerada a partir de um modelo desenvolvido com os principais tipos de requisições que caracterizam um site de e-commerce. Foram realizadas simulações no sistema com diversas combinações de algoritmos de escalonamento e disciplinas de atendimentos para filas, dentre as quais de destaca uma nova disciplina que utiliza um mecanismo de prioridades orientado ao consumo de CPU proposto neste trabalho. O objetivo é aumentar o throughput de requisições de transação e melhorar os tempos de resposta em situações de sobrecarga. Uma avaliação de desempenho foi realizado e constatou-se que o mecanismo de prioridades proposto é adequado às necessidades de um site de e-commerce. / The appearance of new services and applications based on the web has causing a wild increase in the amount of users of the World Wide Web that becomes more popular in the business world. E-commerce sites that demand great request traffic has adopted a distributed web servers system, such as the Web Cluster. This occurs because this sites frequently are on overloaded situations, leaving to serve request transactions (with large probability of generate income) due to increasing demand of navigation requests (generates income only indirectly). The low resource utilization can compromise the system performance. This work is inserted in this context. In this master thesis has been developed a Web server model for E-Commerce (WSE-C). It is validated with a simulation model using a synthetic workload characterized with the main types of equest identified from e-commerce sites. Several simulations were accomplished in the system, combining the scheduling algorithms, the queue attendances disciplines and the use of a new priority mechanism oriented to the CPU utilization. The aim of this work is increase the request throughput and to obtain a better response time on overload situation. A performance evaluation was conducted and shown that priority mechanisms is adequate to a e-commerce site.

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published_or_final_version / abstract / toc / Computer Science and Information Systems / Master / Master of Philosophy

The usage of Web sites has been of interest to Web administrators and researchers ever since the Web started. Analysis of Web site usage data helps to understand the behaviour of its users, which is very important, as many important decisions can be made based on it. The user behaviour may be deduced by knowing all the activities each user does from the time s/he starts a session on the Web site until s/he leaves it, which is collectively called a user session. As Web server logs explicitly record the browsing behaviour of site users and are readily and economically available, this thesis explores the use of Web server logs in capturing user sessions on Web. In order to protect users’ privacy, the standard Web server logs in general do not record the user identities or similar measures to uniquely identify the users. This thesis concentrates on heuristic strategies to infer user sessions. The heuristics exploit the background knowledge of user navigational behaviour recorded in the standard Web server logs without requiring additional information through cookies, logins and session ids. They identify relationships that may exist among the log data and make use of them to assess whether requests registered by the Web server can belong to the same individual and whether these requests were performed during the same visit. Researchers have proposed several heuristics, which were adversely affected by proxy servers, caching and undefined referrers. The thesis proposes new heuristics, which effectively address all the limitations, thus extending the work in this field. It also introduces a set of measures to quantify the performance of the heuristics and uses them to investigate their efficiency based on logs from three Web sites and makes recommendations for the Web sites to devise their own heuristics. The investigation has shown satisfactory results and the new heuristics are applicable to wider range of Web sites. / Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 53-57). Also available on the World Wide Web.

Thesis (M.S.)--Ohio University, June, 2001. / Title from PDF t.p.

Thesis (Ph. D.)--West Virginia University, 1998. / Title from document title page. Document formatted into pages; contains xvii, 90 p. : ill. Vita. Includes abstract.

Thesis (M.S. in Information Technology Management)--Naval Postgraduate School, September 2002. / Thesis advisor(s): William J. Haga, Gary Porter. Includes bibliographical references (p. 63). Also available online.

Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη μιας υπηρεσίας τηλεματικής για την σωστή διαχείριση δεδομένων φαρμακευτικής αγωγής σε χρόνιες παθήσεις. Συγκεκριμένα, έγινε ανάπτυξη ενός συστήματος το οποίο θα μπορεί να χρησιμοποιεί ο ασθενής που λαμβάνει τη φαρμακευτική αγωγή καθώς και ο γιατρός που τον παρακολουθεί. Δημιουργήθηκε ένας server και με τη βοήθεια μιας βάσης δεδομένων και ενός web interface, το οποίο στην περίπτωσή μας είναι ένα website, είναι δυνατή η άμεση παρακολούθηση και καταχώρηση της φαρμακευτικής αγωγής του κάθε ασθενή σύμφωνα με τις οδηγίες του επιβλέποντα ιατρού. Στα πλαίσια της προσπάθειας αυτής, αναπτύχθηκε ολοκληρωμένο υπολογιστικό σύστημα σε γραφικό περιβάλλον ως λογισμικό πακέτο σε γλώσσα java με τη βοήθεια των προγραμμάτων IIS, Microsoft Visual Studio 2003, Sql Server (Enterprise edition). To website μπορεί να χρησιμοποιηθεί παράλληλα από τον ασθενή, τον ιατρό και τον εκάστοτε administrator. Ο κάθε χρήστης ανάλογα με την ιδιότητά του έχει και τις ανάλογες επιτρεπτές χρήσεις του site. Η λειτουργικότητα επίσης αυτής της μεθοδολογίας βασίζεται και στην άμεση επικοινωνία που θα μπορεί μελλοντικά να έχει ο web server με την κάθε φαρμακευτική συσκευή. Η μεθοδολογία αυτή μπορεί να γίνει οδηγός για την πραγματοποίηση και ενσωμάτωση περαιτέρω εφαρμογών και δυνατοτήτων μέσω του server με απλές αλλαγές στον κώδικα και στο γραφικό περιβάλλον. / The scope of this thesis was the development of a service of Σelematics for the correct management of data of pharmaceutical treatment in chronic diseases. More precisely, the growth of system that might be used by the patient that receives the pharmaceutical education as well as the doctor that watches him was developed. A server was created and with the aid of a database and a Web Interface, that in our case is a Website, the direct follow-up and registration of pharmaceutical care of each patient according to the directions of the supervising doctor was achieved. In the frames of this effort, a completed software system in graphic environment programmed in language Java with the help of programs IIS, Microsoft Visual Studio 2003, Sql Server (Enterprise Edition) was developed. The Website can be used at the same time from the patient, the doctor and each administrator. Each user depending on his attribute has also the proportional permissible uses of Site. The functionalism of this methodology is also based on the direct communication that it might in future have Web server with each pharmaceutical appliance. This methodology can become useful of further applications and possibilities via Server with simple changes in the code and in the graphic environment.