Monitoring QoS parameters of composed web services

An Service Level Agreement (SLA) is a contract between service provider and consumer, and includes appropriate actions to be taken upon violation of the contractual obligations. To ensure the negotiation on an SLA is reasonable by reference the measured history data. The paper proposes a feasible Web Service Level Agreement (WS-SLA) Establishing Framework, which can flexible define trustable SLA requirements and penalties actions upon service providers based on monitoring data from service consumer. Web service QoS (WS-QoS) Monitor provides the automatic approach for measureing Quality of Service (QoS) parameters from service requester side. WS-SLA Editor allows service consumer to flexible define their SLA requirement and penalties actions upon service providers.

Managing Service Level Agreement (SLA) for composite semantic web services is a very complex process, as it involves many complex tasks such as components discovery, provisioning, monitoring, recovery, and coordination. Indeed, managing all these tasks manually is a very cumbersome operation, nevertheless it is time consuming and prone to errors. To overcome such problems, automated SLA management for composite semantic web services is needed. This requires the SLA of the composite service to be described in a machine-understandable format such that it can be understood and processed by the automated SLA management tool. Currently, there is no SLA description language for composite semantic web services, but there exists an SLA description language for atomic web services, known as the Web Service Level Agreement (WSLA). Hence, in this paper, we aim to extend the WSLA language to describe composite semantic web services' SLAs, then we show how we can automatically generate the components' SLAs from the composite semantic web services' SLAs; adopting the CRECENT framework that we previously proposed for managing composite web services.

Service level agreement (SLA) is a formal contract between a service provider and a service consumer to guarantee the Quality of service (QoS) expectations, it is used in all areas of information technology, such as Cloud Computing, Internet of Things (IoT), networks and Web services. For IoT applications, the main challenges are: (1) how to describe the SLA terms, such as QoS properties, service levels, penalties in SLA violation, (2) how to monitor these terms, and (3) how to integrate an SLA into all the IoT application layers. Therefore, in this paper, we propose ML-SLA-IoT, a framework for SLA specification and monitoring. It covers the entire layers of an IoT application. It describes precisely QoS levels, provided services, and obligations. It differs from other SLA specification languages in the specification of user preferences, the use of microservices (for reusability, dynamism and ease of integration) and ML-SLA (multi-level metrics and QoS according to existing constraints and user preferences). Furthermore, ML-SLA-IoT monitors SLA terms in an automatic and decentralised manner using smart contracts and blockchain technologies without the intervention of the third-party. Finally, we present a comparative study and experiments with existing solutions regarding to some criteria for SLA specification and monitoring. Our results show that ML-SLA-IoT gives better performance in terms of dynamic pricing, obligation combination, and SLA monitoring.

Monitoring Quality of Service (QoS) compliance is an important procedure in web service environment. It determines whether users' expectations are met, and becomes the vital factor for them to decide whether to continue paying for the service or not. The monitoring is performed by checking the actual services performance against the QoS stated in Service Level Agreement (SLA). In relation to that, the need for monitoring vague QoS specifications in SLA has become more apparent nowadays. This paper reviews the published literature on web services QoS monitoring. A total of 60 selected articles were systematically analyzed. There were 23 of the articles selected through restrictive search criteria while the other 37 were selected based on unrestrictive search criteria. The review shows that little evidence exists on monitoring vague QoS specifications of web services. Providing ability for monitoring QoS that is specified vaguely in SLA could give new insights and implications to web services field. This paper concludes with some recommended future works to construct the theory and perform the empirical research.

In the Web Service Composition (WSC) domain, Web Services (WSs) execute in a highly dynamic environment, as a result, the Quality of Service (QoS) of a WS is constantly evolving, and this requires tracking of the global optimization overtime to satisfy the users’ requirements. In order to make a WSC adapt to such QoS changes of WSs, we propose a self-healing model for WSC. Self-healing is the automatic discovery, and healing of the failure of a composite WS by itself due to QoS changes without interruption in the WSC and any human intervention. To the best of our knowledge, almost all the existing self-healing models in this domain substitute the faulty WS with an equivalent one without paying attention to the WS selection processes to achieve global optimization. They focus only on the WS substitution strategy. In this paper, we propose a self-healing model where we use our hybrid approach to find the optimal WSC by using Parallel Genetic Algorithm based on Q-learning, which we integrate with K-means clustering (PGAQK). The components of this model are organized according to IBM’s Monitor, Analyse, Plan, Execute, and Knowledge (MAPE-K) reference model. The PGAQK approach considers as a module in the Execute component. WS substitution strategy has also been applied in this model that substitutes the faulty WS with another equivalent one from a list of candidate WSs by using the K-means clustering technique. K-means clustering is used to prune the WSs in the search space to find the best WSs for the environment changes. We implemented this model over the NET Framework using C# programming language. A series of comparable experiments showed that the proposed model outperforms improved GA to achieve global optimization. Our proposed model also can dynamically substitute the faulty WSs with other equivalent ones in a time-efficient manner

A probabilistic approach to modeling and estimating the QoS of web-services-based workflows

웹 서비스의 활용 범위가 커지고 실제적인 구현사례가 늘어감에 따라, 웹 서비스 품질모델을 현실적으로 적용할 수 있는 방법에 대한 중요성이 커지고 있다. 웹 서비스 품질을 일관성있게 유지하기 위해서는 웹 서비스 품질보증에 대한 방안이 연구되어야만 한다. 웹 서비스 보증이란 웹 서비스의 품질수준을 일정수준이상으로 유지하기 위한 행위들의 총체를 의미하며, 이를 위해 웹 서비스 품질보증자란 새로운 개념의 관계자가 국제기구에서 웹 서비스 표준으로 새롭게 제시되었다. 웹 서비스 품질보증자는 웹 서비스 사용자들의 품질요구사항을 수렴하여, 웹 서비스 제공자가 일정 품질수준이상의 웹 서비스를 제공할 수 있도록 감시한다. 웹 서비스 제공자와 사용자 그리고, 품질보증자는 웹 서비스 수준을 관리하기 위해 서비스 수준을 측정하여 그 결과에 따라 페널티와 인센티브를 부여하는 SLA(Service Level Agreement) 방식을 적용할 수 있다. 하지만, SLA에서는 서비스 사용자와 제공자가 같은 서비스 항목에 대해 일대일로 대응한다는 전제를 가지고 있어서, 다수사용자와 공공성, 그리고 제3자 관리와 같은 웹 서비스 프레임워크에는 적합하지 않은 점들이 존재한다. 따라서, 웹 서비스에 SLA를 적용하기 위해서는 웹 서비스의 이러한 특성들을 반영한 새로운 보증기법이 필요하다. 본 논문에서는 품질 기대수준을 표현하기 위해 웹 서비스 품질 위탁보증수준이라는 새로운 개념을 제시하고자 한다. 이는 각 사용자의 각 품질항목별 품질기대수준의 최대치라 할 수 있으며, 웹 서비스 품질관계자에게 일관성있는 품질 뷰를 제공한다. 본 논문에서는 이를 이용해 각 품질관계자가 보다 쉽게 일정 수준이상의 품질수준을 유지할 수 있는 방안에 대해 제시하고자 한다. As the coverage of Web services become wider and the number of implementation cases is growing, the importance of applying the Web services quality model to real world is increased. For maintaining the level of Web services qualify, it should be required to study on assurance method of Web services qualify level. Assurance for Web services, which is newly proposed by OASIS TC, means the totality of activities for managing the quality level of them. For managing Web service quality, Web service associates could usually use SLA(Service Level Agreement) method in which a service consumer contracts for some service level with a service provider and gives for penalty or pays incentives according to the result of evaluation of services. But, there are some difficulties in applying SLA to Web services, because Web services have publicity, multiple users, and 3rd party for management. So, we need a new assurance method for Web service by considering the characteristics of Web services. This paper provides the new concept of committed assurance level for Web services. This concept can be defined as the set of maximum level of quality expected by each user, which provide the consistent view of Web service quality. This paper presents the method for duality associates to preserve some quality level of Web service by using this concept.

Today, the service computing research is focusing on providing efficient solutions to the challenges of the future Internet applications. The major difference that is created by these applications is their ubiquitous on-the-move availability as cloud services. This means that the mobility is rapidly becoming a fundamental requirement of the future. In addition to that, the integration of mobile and service computing domains has enabled the existing mobile devices to offer their resources as mobile Web Services (WS). For this reason, the provisioning of mobile WS in future networks is expected to become a part of the cloud, where ubiquitous services are offered by any device. This will open new business prospects for the service providers. In this paper, we present the concept of protecting such mobile WS by using Service Level Agreements (SLA) on mobile devices. Here, we propose a framework to offer SLA negotiations and manage the Quality of Service (QoS) of the provisioned mobile WS. Furthermore, the paper explains the four primary architectural components and classifies their functions into four fundamental SLA life cycles. Also, the detailed discussion regarding each life cycle and its relation to the corresponding component(s) is provided. The research addresses some major issues of authentic and authorized access to mobile WS that might become useful as we move towards the future ubiquitous Internet.

Business-to-Business (B2B) applications are developed predominantly based on service-oriented architectural style which is generally realized using a set of loosely coupled web services. These web services can be selected statically during design-time or dynamically during run-time. The functional and non-functional QoS requirements are typically captured in the Service Level Agreement (SLA) that is mutually agreed between the service provider and the service consumer. Whenever an SLA violation happens, the service provider incurs a penalty. In order to minimize such penalties, the application that is built through a design-time composition of web services needs to be monitored. Whenever a violation of SLA is predicted, those statically composed web services are dynamically reconfigured. This is called as dynamic reconfiguration in SOA. In this case, even the alternate service selection happens at design-time itself. On the other hand, whenever the web services needed for an SOA application development are selected and composed dynamically at run-time, it is called as dynamic composition. The turnaround time involved in both these approaches for mission-critical applications with stringent SLA requirements is compared. It has been inferred that the dynamic reconfiguration approach not only maintained the turnaround time always within the accepted limits, it also incurred only less overhead when compared to dynamic composition approach.

A service level agreement (SLA) is part of a contract between a cloud service provider (CSP) and a cloud service user (CSU) which defines and describes different agreed properties of the service. The negotiation of the SLA between a CSU and a CSP is a pivotal process in the SLA life cycle. An SLA may include many negotiable quality of service (QoS) parameters with each QoS parameter having multiple acceptable values. Different combinations of acceptable values for all QoS parameters grow exponentially as number of QoS parameters and their selectable values increase. Manually negotiating for all of the QoS parameters considering their various options can be an erroneous and diligent task with lower utility. In this paper, a time efficient flip-flop negotiation strategy for the SLAs in cloud services is presented. The flip-flop negotiation strategy is based on a time dependent 3D utility function and on a dynamic concession strategy using the polynomial extrapolation of opponent's concession. This negotiation strategy is useful for time-critical cloud services as it operates with a motive of reaching an agreement at earlier time without compromising over the utility level of the agreement. Moreover, a multi-provider concurrent negotiation method is presented in this work using the flip-flop negotiation strategy. Multiple experiments are performed (using the implementation of flip-flop negotiation strategy) to test the presented work. The results of the experiments enforce the validity of the flip-flop negotiation strategy for such cloud services where time is an important factor during the SLA negotiation process.

How to assure Quality of Service (QoS) of the third-party services is very important for the SOA. Effective monitoring technique towards QoS, which is an important measurement for third-party service quality, is necessary to ensure quality of Web service. Current monitoring approaches do not consider the influences of environment factors such as the position of server, user usage, and the load at runtime. Ignoring these influences, which do exist among the monitoring process, may cause existing monitoring approaches producing unpredictable monitoring results. In order to overcome this limitation, this paper proposes a novel Web Service QoS (WS-Qos) monitoring approach sensitive to environmental factors called weighted Bayesian Runtime Monitor (wBSRM) based on weighted naïve Bayesian classifiers and Term Frequency-Inverse Document Frequency (TF-IDF) algorithm. wBSRM constructs weighted naïve Bayesian classifier by learning a part of samples to classify the monitoring results. The results meeting QoS standard are classified as [Formula: see text] and the one that does not meet is classified as [Formula: see text]. Classifier can also output ratio between posterior probability of [Formula: see text] and [Formula: see text], and consequently the analysis can lead to three monitoring results including [Formula: see text], [Formula: see text] or inconclusive. A set of dedicated experiments are conducted to validate wBSRM. The experiments are based on a public dataset and a simulated dataset under the given standard. The experimental results demonstrate that wBSRM is better than previous approaches.

Virtual enterprise is a temporary network of independent companies or enterprises that can quickly bring together to fulfill a value-added task. With the development of Web service technologies, the enterprise business systems can be encapsulated as Web services. Establishing a virtual enterprise is actually a process of Web services composition. As more and more Web services are available, many Web services with different quality of service (QoS) can be found for tasks of the composite Web service. Thus, a significant research problem in Web service composition is how to select the correct Web services for tasks such that the composite Web service gives the best overall quality. In this paper, we propose an approach to achieve Web services selection efficiently with excellent comprehensive quality. Firstly, a comprehensive evaluation model based on generic QoS (GQoS) and domain QoS (DQoS) of composite Web service is established. Secondly, a novel optimization algorithm named culture max–min ant system (C-MMAS) is constructed to solve the problem of Web service selection based on DGQoS. Simulations show that when used in Web service selection, C-MMAS is better than ant colony optimization algorithm and MMAS in efficiency.

To deal with the problems such as Web Services selection algorithm, availability of Web Services composition and QoS(Quality of Service) guarantee, presents a model for Web Services composition based on QoS and providers' benefit. In this model, the traditional UDDI is expanded to describe the QoS attributes of Web Services. A Service Proxy role is added into this model. All Web Services compositions requested by service consumers are fond, bound and invoked by the Service Proxy role. In order to maximize services providers' benefit, presents a Service Request Queue Scheduling algorithm in the Service Proxy role. This model meets the QOS requirements of service consumers, guarantees the availability of Web Services composition and maximizes service providers' benefit. Experimental results confirm the efforts of this model.

A web service is an interface of the software component that can be accessed by standard Internet protocols. The web service technology enables an application to application communication and interoperability. The increasing number of web service providers throughout the globe have produced numerous web services providing the same or similar functionality. This necessitates the use of tools and techniques to search the suitable services available over the Web. UDDI (universal description, discovery and integration) is the first initiative to find the suitable web services based on the requester's functional demands. However, the requester's requirements may also include non-functional aspects like quality of service (QoS). In this paper, the authors define a QoS model for QoS aware and business driven web service publishing and selection. The authors propose a QoS requirement format for the requesters, to specify their complex demands on QoS for the web service selection. The authors define a tree structure called quality constraint tree (QCT) to represent the requester's variety of requirements on QoS properties having varied preferences. The paper proposes a QoS broker based architecture for web service selection, which facilitates the requesters to specify their QoS requirements to select qualitatively optimal web service. A web service selection algorithm is presented, which ranks the functionally similar web services based on the degree of satisfaction of the requester's QoS requirements and preferences. The paper defines web service provider qualities to distinguish qualitatively competitive web services. The paper also presents the modelling and selection mechanism for the requester's alternative constraints defined on the QoS. The authors implement the QoS broker based system to prove the correctness of the proposed web service selection mechanism.

The IT industry is beginning to mirror a trend of specialization and outsourcing that has been present for decades in other industries, such as the automotive industry. We are beginning to see the emergence of specialist service providers, such as CRM services and market places, payment and settlement services, bill presentment services and many others. Organizations increasingly use these services in complex enterprise application systems using web service infrastructures. Unlike the automotive industry, however, the IT industry does not yet have an agreed way to manage web service quality. In this talk, I will focus on managing the service quality of web services that are used across organizational boundaries. I discuss the systematic definition of formal service level agreement languages that support the precise definition of service quality, such as latency, throughput, availability and reliability. I present how service level agreements written in these languages can be used and describe how service level agreements can be policed. I conclude the talk by sketching further research that is necessary before we have a similar grip on quality as other engineering disciplines.