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

A specification-based QoS-aware design framework for service-based applications

Effective and accurate service discovery and composition rely on complete specifications of service behaviour, containing inputs and preconditions that are required before service execution, outputs, effects and ramifications of a successful execution and explanations for unsuccessful executions. The previously defined Web Service Specification Language (WSSL) relies on the fluent calculus formalism to produce such rich specifications for atomic and composite services. In this work, we propose further extensions that focus on the specification of QoS profiles, as well as partially observable service states. Additionally, a design framework for service-based applications is implemented based on WSSL, advancing state of the art by being the first service framework to simultaneously provide several desirable capabilities, such as supporting ramifications and partial observability, as well as non-determinism in composition schemas using heuristic encodings; providing explanations for unexpected behaviour; and QoS-awareness through goal-based techniques. These capabilities are illustrated through a comparative evaluation against prominent state-of-the-art approaches based on a typical SBA design scenario

Learning Services Based on Formal Concept Reasoning

A formal foundation of automated service discovering for Semantic Web is proposed. The approach is based on the formalization of the problem using an agent oriented programming language (ConGolog), as well as on the use of the Formal Concept Analysis as a tool for knowledge extraction.Ministerio de Educación y Ciencia TIN 2004- 0388

State-of-the-art on evolution and reactivity

This report starts by, in Chapter 1, outlining aspects of querying and updating resources on the Web and on the Semantic Web, including the development of query and update languages to be carried out within the Rewerse project. From this outline, it becomes clear that several existing research areas and topics are of interest for this work in Rewerse. In the remainder of this report we further present state of the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs; in Chapter 4 event-condition-action rules, both in the context of active database systems and in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks

Context Aware Web-Service Monitoring

Monitoring the correct behaviour of a service-based system is a necessity and a key challenge in Service Oriented Computing. Several efforts have been directed towards the development of approaches dealing with the monitoring activity of service-based systems. However, these approaches are in general not suitable when dealing with modifications in service-based systems. Furthermore, existing monitoring approaches do not take into consideration the context of the users and how this context may affect the monitor activity. Consequently, a holistic monitor approach, capable of dealing with the dynamic nature of service-based systems and of taking into consideration the user context, would be highly desirable. In this thesis we present a monitor adaptation framework capable of dealing with changes in a service-based system and different types of users interacting with it. More specifically, the framework obtains a set of monitor rules, necessary to verify the correct behaviour of a service-based system, for a particular user. Moreover, the monitor rules verifying the behaviour of a service-based system relate to properties of the context types defined for a user. The main contributions of our work include the general characterisation of a user interacting with a service-based system and the generation of suitable monitor rules.The proposed framework can be applied to any service composition without the need of further modifications. Our work complements previous research carried on in the area of web service monitoring. More specifically, our work generates a set of suitable monitor rules - related to the user context - which are deployed in a run-time monitor component. Our framework has been tested and validated in several cases considering different scenarios

Vers une plateforme dédiée à la composition automatique et l'exécution de services : Applications E-Tourisme

Recently, distributed computing systems based on context awareness have been proposing in several domains such as healthcare, logistics and tourism. The study described in this thesis is a part of a broader project of E-Tourism system that provides nomad user, context-aware personalized services. The work of this thesis focuses on the issues raised by web service composition and execution. Web service composition brings benefits of reusing existing services to synthesize the new resulting service that meets users needs. The way to create web service composition normally happens at design time, but this limits choices of services. This thesis presents a novel approach of automated web service composition and execution framework. Our approach aims to compose service operations that fulfill mobile users' requirements expressed in propositional logic and execute the resulting service based on aggregating multi service components. In the proposed framework, we have introduced our planning algorithm based on abstract goal states to search and connect to service operations, by mean of service operation annotations, for an abstract plan. The abstract plan is expected for workflow model of sequencing, paralleling and conditioning among service operations. However, the generated workflow is not in an executable form, this is why we perform the transformation of the workflow into an executable business process. To achieve the business process execution, we defined context based BPMN model for mapping the abstract plan to BPMN semantics. We also propose a new validation algorithm and exploited planning-as-model-checking approach to validate the semantic BPMN model whether it is Well-formed and Well-defined BPMN process. Finally, we implemented the automated service composition and execution framework system in Java platform as a proof of concept. We developed the logical composition and, transformation and validation BPMN algorithms written in Prolog. We have integrated these algorithms into the whole system. From the perspective, we plan to extend our current work and take into account more complex user's scenarios that explicitly and implicitly express other pattern controls and we will also consider the scenarios required for stateful web servicesLes systèmes de services contextualisés ont connu un grand essor ces dernières années dans des domaines variés tels que la santé, la logistique ou bien le tourisme. Cette thèse s'intègre dans un projet plus global, nommé E-Tourism, qui vise à réaliser une plateforme de fourniture de services sensibles au contexte à des utilisateurs en situation de mobilité. Le travail de cette thèse se focalise sur la problématique de composition de services web et de leur exécution. La composition de services web permet la réutilisation de services existants afin d'en faire une synthèse répondant au besoin de l'utilisateur. Cette composition se fait en général au niveau de la phase conceptuelle ce qui limite le choix de services potentiels. Cette thèse présente une nouvelle approche de la composition de services Web automatisé et une plateforme d'exécution. Notre approche vise à composer les opérations de services qui répondent aux besoins des utilisateurs mobiles exprimées dans une logique propositionnelle et exécuter le service composé en agrégeant plusieurs services composants. Nous avons proposé une plateforme d'exécution de services et nous avons introduit un nouvel algorithme de planification intégré à cette plateforme. Nous avons défini un contexte basé sur le modèle BPMN. Afin de valider notre modèle sémantique nous avons utilisé une approche de type « model-checking » . Enfin, nous avons réalisé un prototype sous forme d'une plateforme de composition de services et d'exécution automatique en Java. Nous avons implémenté les règles d'inférence et les modèles BPMN en prolog. Enfin, nous avons intégré ces algorithmes dans l'ensemble du système. En perspectives, nous prévoyons d'étendre notre travail actuel et prendre en compte des scénarios plus complexes nécessitant des services web dynamiques