Khaled Mahbub

A framework for requirents monitoring of service based systems

This paper proposes a framework for monitoring the compliance of systems composed of web-services with requirements set for th. This framework assumes systems composed of web-services that are co-ordinated by a service composition process expressed in BPEL4WS and uses event calculus to specify the properties to be monitored. The monitorable properties may include behavioural properties of a syst which are automatically extracted from the specification of its composition process in BPEL4WS and/or assumptions that syst providers can specify in terms of events extracted from this specification.

Run-time monitoring of requirements for systems composed of Web-services: initial implementation and evaluation experience

This paper describes a framework supporting the runtime monitoring of requirements for systems implemented as compositions of Web-services specified in BPEL. The requirements that can be monitored are specified in event calculus. The paper presents an overview of the framework and describes the architecture and implementation of a tool that we have developed to operationalise it. It also presents the results of a preliminary experimental evaluation of the framework.

NON-INTRUSIVE MONITORING OF SERVICE-BASED SYSTEMS

This paper presents a framework for monitoring the compliance of systems composed of Web-services with requirements set for them at runtime. This framework assumes systems composed of Web-services which are co-coordinated by a service composition process expressed in BPEL and uses event calculus to specify the requirements to be monitored. These requirements may include behavioral properties of a system which are automatically extracted from the specification of its composition process in BPEL and/or assumptions that system providers can specify in terms of events extracted from this specification.

Monitoring WS-Agreement s: An Event Calculus–Based Approach

In this chapter, we present a framework that we have developed to support the monitoring of service level agreements (SLAs). The agreements that can be monitored by this framework are expressed in an extension of WS-Agreement that we propose. The main characteristic of the proposed extension is that it uses an event calculus–based language, called EC-Assertion, for the specification of the service guarantee terms in a service level agreement that need to be monitored at runtime. The use of EC-Assertion for specifying service guarantee terms provides a well-defined semantics to the specification of such terms and a formal reasoning framework for assessing their satisfiability. The chapter describes also an implementation of the framework and the results of a set of experiments that we have conducted to evaluate it.

The SERENITY Runtime Monitoring Framework

This chapter describes SERENITY’s approach to runtime monitoring and the framework that has been developed to support it. Runtime monitoring is required in SERENITY in order to check for violations of security and dependability properties which are necessary for the correct operation of the security and dependability solutions that are available from the SERENITY framework. This chapter discusses how such properties are specified and monitored. The chapter focuses on the activation and execution of monitoring activities using S&D Patterns and the actions that may be undertaken following the detection of property violations. The approach is demonstrated in reference to one of the industrial case studies of the SERENITY project.

Requirements monitoring for service-based systems: towards a framework based on event calculus

This work proposes a framework for run-time monitoring of the compliance of systems composed of Web-services with requirements set for them. The framework assumes systems composed of Web-services which are coordinated by a service composition process expressed in BPEL4WS and uses event calculus to specify the requirements to be monitored. These requirements include behavioural properties of the system which are automatically extracted from the specification of its composition process in BPEL4WS and/or assumptions that system providers can specify in terms of events extracted from this specification. Requirements are checked using a variant of techniques for checking integrity constraints against temporal deductive databases.

Proactive SLA Negotiation for Service Based Systems

In this paper we propose a framework for proactive SLA negotiation that integrates this process with dynamic service discovery and, hence, can provide integrated runtime support for both these key activities which are necessary in order to achieve the runtime operation of service based systems with minimised interruptions. More specifically, our framework discovers candidate constituent services for a composite service, establishes an agreed but not enforced SLA and a period during which this pre-agreement can be activated should this become necessary.

A monitoring approach for runtime service discovery

Effective runtime service discovery requires identification of services based on different service characteristics such as structural, behavioural, quality, and contextual characteristics. However, current service registries guarantee services described in terms of structural and sometimes quality characteristics and, therefore, it is not always possible to assume that services in them will have all the characteristics required for effective service discovery. In this paper, we describe a monitor-based runtime service discovery framework called MoRSeD. The framework supports service discovery in both push and pull modes of query execution. The push mode of query execution is performed in parallel to the execution of a service-based system, in a proactive way. Both types of queries are specified in a query language called SerDiQueL that allows the representation of structural, behavioral, quality, and contextual conditions of services to be identified. The framework uses a monitor component to verify if behavioral and contextual conditions in the queries can be satisfied by services, based on translations of these conditions into properties represented in event calculus, and verification of the satisfiability of these properties against services. The monitor is also used to support identification that services participating in a service-based system are unavailable, and identification of changes in the behavioral and contextual characteristics of the services. A prototype implementation of the framework has been developed. The framework has been evaluated in terms of comparison of its performance when using and when not using the monitor component.

Translation of SLAs into Monitoring Specifications

The general architecture of the SLA@SOI framework supports the integration of different types of generic or special-purpose monitoring engines. While internally these engines may realise different monitoring approaches (or reasoning mechanisms), externally they support the same common interface. This interface enables the reasoning engines to receive the SLA guarantee terms that need to be monitored and to report monitoring results to the SLA@SOI framework. However, due to differences in the languages that the monitoring engines use to express operational monitoring specifications, the monitoring of SLAs expressed in the SLA specification language of SLA@SOI requires the translation of these SLAs into operational monitoring specifications. This chapter describes the translation scheme developed for the monitoring engine EVEREST, which has been used in the SLA@SOI framework for monitoring SLAs at the software service layer.

Replacement policies for service-based systems

The need to change service-based systems during their execution time has been recognized as an important challenge in service oriented computing. There are several situations that may trigger changes in service-based systems such as unavailability or malfunctioning of services; changes in the functional, quality, or contextual characteristics of the services; changes in the context of the service-based system environment; emergence of new services; or changes in the requirements of the system. However, in order to support dynamic changes in service-based systems, it is necessary to have replacement policies describing what needs to be changed, and how and when the changes should be executed. In this paper, we describe replacement policies to support dynamic changes in service-based systems. These replacement policies are used in our service discovery framework that supports proactive identification of services in parallel to the execution of the system. A prototype tool has been implemented in order to illustrate and evaluate the framework. The results of some initial evaluation are also described in the paper.