Decision support for personalized cloud service selection through multi-attribute trustworthiness evaluation

Facing a customer market with rising demands for cloud service dependability and security, trustworthiness evaluation techniques are becoming essential to cloud service selection. But these methods are out of the reach to most customers as they require considerable expertise. Additionally, since the cloud service evaluation is often a costly and time-consuming process, it is not practical to measure trustworthy attributes of all candidates for each customer. Many existing models cannot easily deal with cloud services which have very few historical records. In this paper, we propose a novel service selection approach in which the missing value prediction and the multi-attribute trustworthiness evaluation are commonly taken into account. By simply collecting limited historical records, the current approach is able to support the personalized trustworthy service selection. The experimental results also show that our approach performs much better than other competing ones with respect to the customer preference and expectation in trustworthiness assessment. © 2014 Ding et al

Probabilistic QoS and Soft Contracts for Transaction-Based Web Services Orchestrations.

International audienceService level agreements (SLAs), or contracts, have an important role in web services. They define the obligations and rights between the provider of a web service and its client, about the function and the Quality of the service (QoS). For composite services like orchestrations, contracts are deduced by a process called QoS contract composition, based on contracts established between the orchestration and the called web services. Contracts are typically stated as hard guarantees (e.g., response time always less than 5 msec). Using hard bounds is not realistic, however, and more statistical approaches are needed. In this paper we propose using soft probabilistic contracts instead, which consist of a probability distribution for the considered QoS parameter--in this paper, we focus on timing. We show how to compose such contracts, to yield a global probabilistic contract for the orchestration. Our approach is implemented by the TOrQuE tool. Experiments on TOrQuE show that overly pessimistic contracts can be avoided and significant room for safe overbooking exists. An essential component of SLA management is then the continuous monitoring of the performance of called web services, to check for violations of the SLA. We propose a statistical technique for run-time monitoring of soft contracts

Mapeamento de conflitos entre atributos de QoS na monitoração de aplicações SOA

Orientador: Cecília Mary Fischer RubiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: O número de serviços Web funcionalmente similares tem crescido na Web, tornando a qualidade do serviço o seu maior diferencial. A fim de medir o nível de qualidade dos serviços Web, ferramentas de monitoramento tem surgido como um componente essencial que coleta valores das métricas definidas para atributos de qualidade com o objetivo de controlar o nível de qualidade do serviço. Desde que os clientes precisem monitorar mais de um atributo de qualidade ao mesmo tempo, os valores da qualidade do serviço tendem a mudar durante seu monitoramento, podendo produzir conflitos entre eles. Nós dizemos que dois ou mais atributos de qualidade estão em conflito quando existe uma interferência, incompatibilidade ou contradição entre eles, produzindo uma degradação nos valores da qualidade de pelo menos um dos atributos. Para dar solução a esse problema, estudos sistemáticos tem sido realizados a fim de construir catáogos de conflitos entre requisitos não-funcionais. Porém, esses catálogos são usados durante a fase de análise e projeto do ciclo de desenvolvimento de software. Nos últimos anos, serviços REST têm sido usados cada vez mais em sistemas distribuídos modernos. Porém, serviços SOAP ainda são preferidos em sistemas complexos, por causa da segurança oferecida. Esta dissertação realiza uma avaliação experimental, a fim de identificar conflitos potenciais entre atributos de qualidade durante o monitoramento de serviços Web SOAP. Para esse efeito, um experimento e um estudo de caso foram executados, sobre um conjunto de atributos de qualidade pré-selecionados com suas respectivas métricas. Os resultados da avaliação experimental validam conflitos identificados em estudos prévios; porém, encontramos conflitos que não foram mencionados previamente. Foi constado que a causa mais comum de degradação na qualidade dos serviços, foi a falta de memória para processar quantidades grandes de pedidosAbstract: The number of functionally similar web services are increasing on the web, making the quality of service its biggest differential. In order to measure the quality level of web services, monitoring tools have become an essential component, collecting values of metrics to control the quality levels of Web services. Since customers require to monitor more than one attribute at the same time, quality attributes are prone to change in their values during monitoring time, producing conflicts between them. We define that two or more quality attributes are in conflict when there is an interference, incompatibility or contradiction with each other, producing a degradation in the quality values for at least one attribute. To solve this problem, many systematic studies have been performed in order to construct catalogues about conflicts between non-functional requirements during the analysis and design stages of systems development lifecycle. Recently, REST services are being used increasingly in modern systems. However, SOAP services are still preferred in large systems because of their provided security. This dissertation conducts a practical experimentation in order to discover potential conflicts between quality attributes during SOAP services monitoring. For this purpose, two experimental evaluations were conducted, an experiment and a case study were conducted using a set of selected quality attributes with their metrics. The results of the experimental evaluations validated the existing conflicts defined in previous studies; additionally, we detected potential conflicts which were not identified in previous studies. It was also identified that the most common cause of degradation of the quality level of Web services, was the lack of memory for processing a lot of requestsMestradoCiência da ComputaçãoMestre em Ciência da Computação162280/2015-7CAPESCNP

Dynamic Formation and Strategic Management of Web Services Communities

In the last few years, communities of services have been studied in a certain numbers of proposals as virtual pockets of similar expertise. The motivation is to provide these services with high chance of discovery through better visibility, and to enhance their capabilities when it comes to provide requested functionalities. There are some proposed mechanisms and models on aggregating web services and making them cooperate within their communities. However, forming optimal and stable communities as coalitions to maximize individual and group efficiency and income for all the involved parties has not been addressed yet. Moreover, in the proposed frameworks of these communities, a common assumption is that residing services, which are supposed to be autonomous and intelligent, are competing over received requests. However, those services can also exhibit cooperative behaviors, for instance in terms of substituting each other. When competitive and cooperative behaviors and strategies are combined, autonomous services are said to be "coopetitive". Deciding to compete or cooperate inside communities is a problem yet to be investigated. In this thesis, we first identify the problem of defining efficient algorithms for coalition formation mechanisms. We study the community formation problem in two different settings: 1) communities with centralized manager having complete information using cooperative game-theoretic techniques; and 2) communities with distributed decision making mechanisms having incomplete information using training methods. We propose mechanisms for community membership requests and selections of web services in the scenarios where there is interaction between one community and many web services and scenarios where web services can join multiple established communities. Then in order to address the coopetitive relation within communities of web services, we propose a decision making mechanism for our web services to efficiently choose competition or cooperation strategies to maximize their payoffs. We prove that the proposed decision mechanism is efficient and can be implemented in time linear in the length of the time period considered for the analysis and the number of services in the community. Moreover, we conduct extensive simulations, analyze various scenarios, and confirm the obtained theoretical results using parameters from a real web services dataset

INTERVAL TYPE-2 FUZZY MODEL FOR CUSTOMER COMPLAINT HANDLING

Complaint management system (CMS) has become increasingly important for organizations, businesses, and government in Malaysia. The interaction between customers and business provider based on complaints which referring to perceptions and wording involves uncertainties and not an easy task in complaint handling process to rank the complaint

INTERVAL TYPE-2 FUZZY MODEL FOR CUSTOMER COMPLAINT HANDLING

Complaint management system (CMS) has become increasingly important for organizations, businesses, and government in Malaysia. The interaction between customers and business provider based on complaints which referring to perceptions and wording involves uncertainties and not an easy task in complaint handling process to rank the complaint

Bestimmung der Dienstgütezuverlässigkeit in zusammengesetzten Dienstleistungen im Internet der Dienste

Das Anbieten, die Vermittlung und der Konsum von Softwarekomponenten nach dem Paradigma „Software-as-a-Service“ über das Internet wird zunehmend populärer. Diese so genannten elektronischen Dienstleistungen unterschiedlicher Komplexität werden auf Netzwerkservern zur Verfügung gestellt und können von anderen Anwendungen eingebunden werden. Damit können Ressourcen für die Entwicklung und das Betreiben eigener Dienste eingespart werden. Traditionelle Beispiele solcher Dienste sind Währungsumrechnungen oder Wettervorhersagen , aber auch komplexere Geschäftsprozesse, wie z.B. Rechnungsprüfdienste , werden vermehrt als elektronische Dienste bereitgestellt. Voraussetzung für die Akzeptanz der elektronischen Dienstleistungen ist die Absicherung deren Dienstgüte (engl. Quality of Service). Die Dienstgüte gibt Auskunft darüber, wie gut ein Dienst seine Funktion erbringt. Klassische Parameter sind Antwortzeit oder Verfügbarkeit. Die Betrachtung der Dienstgüte hat für den Dienstnutzer als auch für den Dienstanbieter Vorteile: Durch die Angabe der Dienstgüte kann sich der Dienstanbieter von seiner Konkurrenz abgrenzen, während der zukünftige Dienstnutzer in der Lage ist, die Performanz seiner Systeme, welche den Dienst integrieren, abzuschätzen. Beide Parteien streben eine möglichst hohe Dienstgüte an. Die Bestimmung der Dienstgüte in zusammengesetzten Dienstleistungen wurde in den letzten Jahren viel diskutiert. In diesem Zusammenhang ist besonders die Dienstgütezuverlässigkeit eines Dienstes wichtig. Die Dienstgütezuverlässigkeit gibt an, wie sicher es einem Dienst gelingt, seine Qualitätsversprechen einzuhalten. Je nach Kontext spricht man von relativer oder absoluter Dienstgütezuverlässigkeit. Die relative Dienstgütezuverlässigkeit bezieht sich auf die Fähigkeit eines Dienstes seine Dienstgütegarantien während der nächsten Interaktion einzuhalten, während sich die absolute Dienstgütezuverlässigkeit auf den Zeitraum der nächsten n Interaktionen bezieht. Verletzt ein Dienst eine Dienstgütegarantie, weil er beispielsweise nicht in der vorgegebenen Zeit antwortet, so gefährdet der Dienstnutzer die Performanz seiner Systeme, während der Dienstanbieter mit Strafzahlungen zu rechnen hat. Die Bestimmung der Dienstgütezuverlässigkeit einer zusammengesetzten Dienstleistung hat verschiedene Vorteile. Sie gestattet dem Dienstanbieter z.B. drohende Qualitätsverschlechterungen vorherzusagen und auf diese geeignet zu reagieren. Auch der Dienstnutzer profitiert von der Existenz der Dienstgütezuverlässigkeit. Er kann z.B. das Risiko für seine Systeme besser kalkulieren. Ziel dieser Arbeit ist die Bestimmung der Dienstgütezuverlässigkeit in zusammengesetzten Dienstleistungen. Zu diesem Zweck wird die Dienstgütezuverlässigkeit von Teildiensten auf Basis ihrer Monitoring-Historie vorhergesagt. Die Monitoring-Historie protokolliert für jeden Dienst und jede Dienstgütegarantie, ob in vergangenen Interaktionen Dienstgüteverletzungen stattgefundenen haben. Die Dienstgütezuverlässigkeit eines Teildienstes wird als Verletzungswahrscheinlichkeit gemessen, die angibt, wie wahrscheinlich eine Dienstgüteverletzung durch den Teildienst ist. Für die Vorhersage der relativen Verletzungswahrscheinlichkeit kommt eine Markov-Kette erster Ordnung zum Einsatz. Die Bestimmung der absoluten Verletzungswahrscheinlichkeit beruht auf den Prinzipien der allgemeinen Stochastik. Die Berechnungszeit beträgt in beiden Fällen wenige Millisekunden. Beide Verfahren liefern äußerst zuverlässige Vorhersagewerte. Auf Basis der Verletzungswahrscheinlichkeiten der Teildienste wird die Dienstgütezuverlässigkeit der zusammengesetzten Dienstleistung bestimmt. Sie kann detailliert in Form der Verletzungsmatrix oder als einfacher numerischer Wert in Form der Verletzungszahl angegeben werden. Die Verletzungsmatrix einer Dienstgütegarantie enthält die Eintrittswahrscheinlichkeit für jede mögliche Anzahl von Dienstgüteverletzungen. Ihre Aufstellung erfordert exponentiellen Aufwand. Demgegenüber besitzt die Verletzungszahl eine lineare Berechnungszeit. Sie gibt die Belastung einer Dienstleistung mit Dienstgüteverletzungen an. Die Dienstgütezuverlässig ist dabei umso geringer je kleiner die Werte der Verletzungsmatrix und Verletzungszahl sind