Precise service level agreements

SLAng is an XML language for defining service level agreements, the part of a contract between the client and provider of an Internet service that describes the quality attributes that the service is required to possess. We define the semantics of SLAng precisely by modelling the syntax of the language in UML, then embedding the language model in an environmental model that describes the structure and behaviour of services. The presence of SLAng elements imposes behavioural constraints on service elements, and the precise definition of these constraints using OCL constitutes the semantic description of the language. We use the semantics to define a notion of SLA compatibility, and an extension to UML that enables the modelling of service situations as a precursor to analysis, implementation and provisioning activities

Contract Aware Components, 10 years after

The notion of contract aware components has been published roughly ten years ago and is now becoming mainstream in several fields where the usage of software components is seen as critical. The goal of this paper is to survey domains such as Embedded Systems or Service Oriented Architecture where the notion of contract aware components has been influential. For each of these domains we briefly describe what has been done with this idea and we discuss the remaining challenges.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Model-driven semantic Web service composition

As the number of available Web services increases there is a growing demand to realise complex business processes by combining and reusing available Web services. The reuse and combination of services results in a composition of Web services that may also involve services provided in the Internet. With semantically described Web services, an automated matchmaking of capabilities can help identify suitable services. To address the need for semantically de-fined Web services, OWL-S and WSML have been proposed as competing semantic Web service languages. We show how the proposed semantic Web service languages can be utilized within a model-driven methodology for build-ing composite Web services. In addition we combine the semantic-based discovery with the support for processing QoS requirements to apply a ranking or a selection of the candidates. The methodology describes a process which guides the developer through four phases, starting with the initial modelling, and ending with a new composite service that can be deployed and published to be consumed by other users.

A Framework for Secure Management of Web Services (SMaWS) in Enterprise Application Integration

This dissertation addresses challenges currently faced by enterprises that have embraced the new technology called Web Service in order to reduce the cost of enterprise application integration (EAI) as well as improve operational efficiency of their mission-critical business processes. The nature of Web Service introduces new challenges such as dependency among applications, and a failure in one application can lead to a failure in other dependent applications. Such challenges have led to a growing need for enterprises to confront Web Service monitoring and management issues as a priority. As a solution, this dissertation proposes a SMaWS (Secure Management of Web Services) infrastructure for secure monitoring and management of Web Services. Its goals are to provide deeper visibility into Web Service runtime activities as compared to currently Web Service management tools; access to information about the Quality of Service (QoS) of these Web Services; and a unified monitoring environment for Web Services deployed across enterprise business units. This enables an earlier detection of poor performance problem in each interdependent Web Service, which would lead to a faster diagnose and fixing of possible performance issue, and thus maximize availability. This dissertation describes the requirements analysis for monitoring and management of Web Services across an enterprise environment. It describes the architecture and design of the SMaWS infrastructure proposed for secure monitoring and management of Web Service. The proposed SMaWS framework enables the instrumentation of existing and newly developed Web Service applications, and extracts Web Service performance statistics. It determines Web Service identity, reliability, availability, security, usage, and license used by Web Service consumers to access a given service. This dissertation describes the SMaWS Repository and Security concepts that are proposed to address the challenges faced by most distributed architectures to enable the client applications determine the location of the server (“bootstrapping problem”), and at the same time ensuring both the integrity and confidentiality of parties involved. Finally, this dissertation presents a prototype implementation of SMaWS Manager Application and Sample SMaWS Web Service applications. The experimental results obtained, in terms of overhead induced by the SMaWS framework on the monitored Web Service applications, demonstrate the feasibility of the SMaWS infrastructure

QoS integration in web services

With the growing popularity of Web services, a general QoS support for Web services will play an important role for the success of this emerging technology. Unfortunately, current Web service environments do not offer comprehensive QoS support. In this paper, we present an approach that does not only enable the QoS integration in Web services, but also the selection of appropriate services based on QoS requirements regarding server and network performance as well as the mapping of QoS requirements onto the underlying QoS aware network at runtime

Differentiating Web Service Offerings

The advent of Service Oriented Architecture (SOA) paradigm and increasing use of Web Services (WS) implies that the future will see a large number of services transferred between providers and consumers, using many applications or agents working on behalf of humans. Discovering and using the services is the easy part. Negotiating and selecting the best services from amongst the plethora of similar ones, depending on their cost and quality, is the challenging issue. However, existing WS-I standards neither cater to provision of Service Level Agreements (SLAs), nor their exchange between parties. These standards are confined merely to WS description (WSDL). Once WS are discovered and selected, SLAs are merely used to monitor service compliance. We propose a novel method that allows service-providers to dynamically generate the SLAs, and then transfer them to clients for selection amongst competitive service providers. The clients use Application to Application (A2A) communication to choose the best service provider at run time, and then bind to it to available services. Our method complies with all WS-I standards, and hence does not require any modifications to the UDDI or WSDL. Instead of using the SLA as just a contractual document for compliance monitoring of the service, we also use it as a means of service selection. We demonstrate and validate our method using a prototype developed in laboratory settings, which uses multiple ‘Weather Service Providers’ to obtain various indicators for weather forecasting

Artificial Intelligence: A Promised Land for Web Services

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