A QoS registry for adaptive real-time service-oriented applications

Real-time service-oriented applications are charac- terized by Quality of Service (QoS) requirements that cannot be properly managed by using classical real-time systems methodologies. In dynamic environments the QoS management can effectively leverage adaptive techniques, that provide flexibility and do not require a complex offline analysis. In turn, such techniques make a massive use of on-line collected data regarding the application performance and the resource requirements. Moreover, a common issue for adaptive systems is the one of deciding the initial configuration of the application and/or the run-time environment at the time of service instantiation. In this paper, we propose a QoS registry for coping with these issues and supporting the configuration of proper scheduling parameters in real-time Service Oriented Architectures (SOAs). The registry permits to gather QoS data related to different functional behaviors of applications, to predict the future trend based on data already collected and to permanently store such data for an effective reuse at the time of future re-instantiations. We have also built an implementation of such registry, computed its overhead costs and performed some experiments for showing the effectiveness in auto-tuning resource allocations for providing QoS guarantees in a real-time SOA

Herramienta para la compensación de parámetros de QoS y seguridad

El análisis conjunto de mecanismos de seguridad y QoS es esencial para las redes heterogéneas donde diversos dispositivos pueden coexistir en entornos dinámicos. En concreto, los dispositivos no siempre pueden ser conocidos, por lo que diferentes requisitos y mecanismos pueden surgir para el análisis. En este artículo, proponemos una herramienta para facilitar la configuración de entornos basada en el análisis paramétrico de dependencias, tomando como base de conocimiento un conjunto de parámetros de seguridad y QoS. Esta forma de análisis de parámetros a alto nivel permite considerar las dependencias y la compensación entre mecanismos con independencia del sistema de información subyacente. Posibilita por tanto evaluar el impacto que tales mecanismos, y otros definidos acorde al modelo, tienen sobre un sistema previo a su despliegue.Este trabajo ha sido parcialmente subvencionado por el Ministerio de Economía y Competitividad a través del proyecto ARES (CSD2007-00004). Adicionalmente, ha sido financiado por la Junta de Andalucía través del proyecto FISICCO (TIC-07223). El primer autor ha sido subvencionado por el Programa FPI

Controlled Components for Internet of Things As-A-Service

In order to facilitate developers willing to create future Internet of Things (IoT) services incorporating the nonfunctional aspects, we introduce an approach and an environment based on controlled components. Our approach allows developers to design an IoT "as-a-service", to build the service composition and to manage it. This is important, because the IoT allows us to observe and understand the real world in order to have decision-making information to act on reality. It is important to make sure that all these components work according to their mission, i.e. their Quality of Service (QoS) contract. Our environment provides the modeling, generates Architecture Description Language (ADL) formats, and uses them in the implementation phase on an open-source platform

Dynamic adaptation of interaction models for stateful web services

Dissertação para obtenção do Grau de Mestre em Engenharia InformáticaWireless Sensor Networks (WSNs) are accepted as one of the fundamental technologies for current and future science in all domains, where WSNs formed from either static or mobile sensor devices allow a low cost high-resolution sensing of the environment. Such opens the possibility of developing new kinds of crucial applications or providing more accurate data to more traditional ones. For instance, examples may range from large-scale WSNs deployed on oceans contributing to weather prediction simulations; to high number of diverse Sensor devices deployed over a geographical area at different heights from the ground for collecting more accurate data for cyclic wildfire spread simulations; or to networks of mobile phone devices contributing to urban traffic management via Participatory Sensing applications. In order to simplify data access, network parameterisation, and WSNs aggregation, WSNs have been integrated in Web environments, namely through high level standard interfaces like Web services. However, the typical interface access usually supports a restricted number of interaction models and the available mechanisms for their run-time adaptation are still scarce. Nevertheless, applications demand a richer and more flexible control on interface accesses – e.g. such accesses may depend on contextual information and, consequently, may evolve in time. Additionally, Web services have become increasingly popular in the latest years, and their usage led to the need of aggregating and coordinating them and also to represent state in between Web services invocations. Current standard composition languages for Web services (wsbpel,wsci,bpml) deal with the traditional forms of service aggregation and coordination, while WS-Resource framework (wsrf) deals with accessing services pertaining state concerns (relating both executing applications and the runtime environment). Subjacent to the notion of service coordination is the need to capture dependencies among them (through the workflow concept, for instance), reuse common interaction models, e.g. embodied in common behavioural Patterns like Client/Server, Publish/- Subscriber, Stream, and respond to dynamic events in the system (novel user requests, service failures, etc.). Dynamic adaptation, in particular, is a pressing requirement for current service-based systems due to the increasing trend on XaaS ("everything as a service") which promises to reduce costs on application development and infrastructure support, as is already apparent in the Cloud computing domain. Therefore, the self-adaptive (or dynamic/adaptive) systems present themselves as a solution to the above concerns. However, since they comprise a vast area, this thesis only focus on self-adaptive software. Concretely, we propose a novel model for dynamic interactions, in particular with Stateful Web Services, i.e. services interfacing continued activities. The solution consists on a middleware prototype based on pattern abstractions which may be able to provide (novel) richer interaction models and a few structured dynamic adaptation mechanisms, which are captured in the context of a "Session" abstraction. The middleware was implemented and uses a pre-existent framework supporting Web enabled access to WSNs, and some evaluation scenarios were tested in this setting. Namely, this area was chosen as the application domain that contextualizes this work as it contributes to the development of increasingly important applications needing highresolution and low cost sensing of environment. The result is a novel way to specify richer and dynamic modes of accessing and acquiring data generated by WSNs.Este trabalho foi parcialmente financiado pelo Centro de Informática e Tecnologias da Informação (CITI), e pela Fundação para a Ciência e a Tecnologia (FCT / MCTES) em projectos de investigaçã

Interim research assessment 2003-2005 - Computer Science

This report primarily serves as a source of information for the 2007 Interim Research Assessment Committee for Computer Science at the three technical universities in the Netherlands. The report also provides information for others interested in our research activities

Accuracy Assessment of forecasting services

English: A service system is a dynamic configuration of people, technologies, organisations and shared information that create and deliver value to customers and other stakeholders [1]. The following cases are examples of customers receiving a service: taking a bus to go somewhere, or going to a restaurant to have a meal, or for a small IT (information technology) company, contracting a service to a bigger one in order to save costs and time. Service-oriented architecture (SOA) has become more popular during last years. Basically, this emerging development paradigm allows service providers to offer loosely coupled services. These services are normally only owned by the providers. As a result, the service user or client does not have to worry about the development, maintenance, infrastructure, or any other issue of how the service is working. To sum up, the user just has to find and choose the proper service. On the one hand, it presents several advantages. Firstly, common functionality can be contracted as a service in order to be able to focus on the own core missions. Secondly, it decreases the cost, since it is cheaper to contract a service than creating it yourself. Thirdly, clients take benefit of provider’s latest technologies. On the other hand, there is one big drawback: lack of trust. When you contract a service, you lose the direct control, the provider has access to your own data, you depend on him, and you experiment delays since your functionality is not working in-home. That is why the user has to decide previously which service is the most appropriate for his needs. Each client has different needs: quality (it varies among services), reputation (a famous or recommended provider usually gives more confidence), speed (agreements not to break thresholds), security (contract and trust in the provider), personalisation (preferential treatment from the provider), and locality (law is not the same in all countries). Therefore, a customer needs to know about the best service(s).Among all kind of services, we concentrate on forecasting services. Forecasting services show in advance a condition or occurrence about the future. There are plenty of domains: weather forecasts, stock market prices, results in betting shops, elections… Let us see a domain which is really familiar to all of us: weather forecast. When we are planning to travel, going somewhere or just deciding what to wear first thing in the morning, we wonder about weather conditions. To make these decisions, we check the weather forecast on TV news, a thermometer, or on a web site. However, sometimes we check several predictions and they do not agree. Which one will be the most accurate? Our goal in this master thesis is to assess the accuracy of these forecasting services in order to help prospective users to choose the best one according to their needs. To do it, we are going to compare forecast predictions with actual real observations

Ontology based contextualization and context constraints management in web service processes

The flexibility and dynamism of service-based applications impose shifting the validation process to runtime; therefore, runtime monitoring of dynamic features attached to service-based systems is becoming an important direction of research that motivated the definition of our work. We propose an ontology based contextualization and a framework and techniques for managing context constraints in a Web service process for dynamic requirements validation monitoring at process runtime. Firstly, we propose an approach to define and model dynamic service context attached to composition and execution of services in a service process at run-time. Secondly, managing context constraints are defined in a framework, which has three main processes for context manipulation and reasoning, context constraints generation, and dynamic instrumentation and validation monitoring of context constraints. The dynamic requirements attached to service composition and execution are generated as context constraints. The dynamic service context modeling is investigated based on empirical analysis of application scenarios in the classical business domain and analysing previous models in the literature. The orientation of context aspects in a general context taxonomy is considered important. The Ontology Web Language (OWL) has many merits on formalising dynamic service context such as shared conceptualization, logical language support for composition and reasoning, XML based interoperability, etc. XML-based constraint representation is compatible with Web service technologies. The analysis of complementary case study scenarios and expert opinions through a survey illustrate the validity and completeness of our context model. The proposed techniques for context manipulation, context constraints generation, instrumentation and validation monitoring are investigated through a set of experiments from an empirical evaluation. The analytical evaluation is also used to evaluate algorithms. Our contributions and evaluation results provide a further step towards developing a highly automated dynamic requirements management system for service processes at process run-time