6,159 research outputs found

    An Approach to Temporal-Aware Procurement of Web Services

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    Es también una ponencia de: International Conference on Service-Oriented Computing: ICSOC 2005: Service-Oriented Computing - ICSOC 2005 pp 170-184. book ISBN: 978-3-540-30817-1 e-ISBN: 978-3-540-32294-8In the context of web service procurement (WSP), temporal–awareness refers to managing service demands and offers which are subject to validity periods, i.e. their evaluation depends not only on quality of service (QoS) values but also on time. For example, the QoS of some web services can be considered critical in working hours (9:00 to 17:00 from Monday to Friday) and irrelevant at any other moment. Until now, the expressiveness of such temporal–aware specifications has been quite limited. As far as we know, most proposals have considered validity periods to be composed of a single temporal interval. Other proposals, which could allow more expressive time–dependent specifications, have not performed a detailed study about all the underlying complexities of such approach, in spite of the fact that dealing with complex expressions on temporality is not a trivial task at all. As a matter of fact, it requires a special design of the so–called procurement tasks (consistency and conformance checking, and optimal selection). In this paper, we present a constraint–based approach to temporal–aware WSP. Using constraints allows a great deal of expressiveness, so that not only demands and offers can be assigned validity periods but also their conditions can be assigned (possibly multiple) validity temporal subintervals. Apart from revising the semantics of procurement tasks, which we previously presented in the first edition of the ICSOC conferences, we also introduce the notion of the covering set of a demand, a topic which is closely related to temporality.Ministerio de Ciencia y Tecnología TIC2003-02737-C02-0

    On User Preferences and Utility Functions in Selection: A Semantic Approach

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    Discovery tasks in the context of Semantic Web Services are generally performed using Description Logics. However, this formalism is not suited when non-functional, numerical parameters are involved in the discovery process. Furthermore, in selection tasks, where an optimization algorithm is needed, DLs are not capable of computing the optimum. Although there are DLs extensions that can handle numerical parameters, they bring decidability problems. Other solutions, as hybrid approaches which use DLs in functional discovery and other formalisms in non-functional selection, do not provide a semantic framework to describe user preferences based on non-functional properties. In this work, we propose to semantically describe user preferences, so they can be used to perform selection within a hybrid solution. By using semantically described utility functions in order to define user preferences, our proposal enables interoperability between service offers and demands, while providing a high level of expressiveness in these preferences and including them within SWS descriptions.Comisión Interministerial de Ciencia y Tecnología TIN2006-0047

    Semantic Web Services Provisioning

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    Semantic Web Services constitute an important research area, where vari ous underlying frameworks, such as WSMO and OWL-S, define Semantic Web ontologies to describe Web services, so they can be automatically discovered, composed, and invoked. Service discovery has been traditionally interpreted as a functional filter in current Semantic Web Services frameworks, frequently performed by Description Logics reasoners. However, semantic provisioning has to be performed taking Quality-of-Service (QOS) into account, defining user preferences that enable QOS-aware Semantic Web Service selection. Nowadays, the research focus is actually on QOS-aware processes, so cur rent proposals are developing the field by providing QOS support to semantic provisioning, especially in selection processes. These processes lead to opti mization problems, where the best service among a set of services has to be selected, so Description Logics cannot be used in this context. Furthermore, user preferences has to be semantically defined so they can be used within selection processes. There are several proposals that extend Semantic Web Services frameworks allowing QOS-aware semantic provisioning. However, proposed selection techniques are very coupled with their proposed extensions, most of them being implemented ad hoc. Thus, there is a semantic gap between functional descriptions (usually using WSMO or OWL-S) and user preferences, which are specific for each proposal, using different ontologies or even non-semantic de scriptions, and depending on its corresponding ad hoc selection technique. In this report, we give an overview of most important Semantic Web Ser vices frameworks, showing a comparison between them. Then, a thorough analysis of state-of-the art proposals on QOS-aware semantic provisioning and user preferences descriptions is presented, discussing about their applicabil ity, advantages, and defects. Results from this analysis motivate our research work, which has been already materialized in two early contributions.Los servicios web semánticos constituyen un importante campo de inves tigación, en el cual distintos frameworks, como por ejemplo WSMO y OWL-S, definen ontologías de la web semántica para describir servicios web, de for ma que estos puedan ser descubiertos, compuestos e invocados de manera automática. El descubrimiento de servicios ha sido interpretado tradicional mente como un filtro funcional en los frameworks actuales de servicios web semánticos, usando para ello razonadores de lógica descriptiva. Sin embargo, las tareas de aprovisionamiento semántico deberían tener en cuenta la calidad del servicio, definiendo para ello preferencias de usuario de manera que sea posible realizar una selección de servicios web semánticos sensible a la cali dad. Actualmente, el foco de la investigación está en procesos sensibles a la ca lidad, por lo que las propuestas actuales están trabajando en este campo intro duciendo el soporte adecuado a la calidad del servicio dentro del aprovisio namiento semántico, y principalmente en las tareas de selección. Estas tareas desembocan en problemas de optimización, donde el mejor servicio de entre un concjunto debe ser seleccionado, por lo que las lógicas descriptivas no pue den ser usadas en este contexto. Además, las preferencias de usuario deben ser definidas semánticamente, de forma que puedan ser usadas en las tareas de selección. Existen bastantes propuestas que extienden los frameworks de servicios web semánticos para habilitar el aprovisionamiento sensible a la calidad. Sin embargo, las técnicas de selección propuestas están altamente acopladas con dichas extensiones, donde la mayoría de ellas implementan algoritmos ad hoc. Por tanto, existe un salto semántico entre las descripciones funcionales (nor malmente usando WSMO o OWL-S) y las preferencias de usuario, las cuales son definidas específicamente por cada propuesta, usando ontologías distin tas o incluso descripciones no semánticas que dependen de la correspondiente técnica de selección ad hoc

    QoS-Aware Semantic Service Selection: An Optimization Problem

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    In order to select the best suited service among a set of discovered services, with respect to QOS parameters, a user have to state his or her preferences, so services can be ranked according to these QOS parameters. Current Se- mantic Web Services ontologies do not support the defini- tion of QOS-aware user preferences, though there are some proposals that extend those ontologies to allow selection based on those preferences. However, their selection algo- rithms are very coupled with user preferences descriptions, which are defined without semantics or at a different seman- tic level than service functionality. In this work, we present a service selection framework that transforms user prefer- ences into an optimization problem where the best service is selected. This framework is based on an ontology that conceptualizes these user preferences. Thus, we use a very expressive solution decoupled with the concrete selection technique by using XSL transformations, while describing QOS-aware user preferences at the same semantic level of functional preferences.Comisión Interministerial de Ciencia y Tecnología TIN2006-00472Junta de Andalucía TIC-253

    Design of Tender Management System

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    One of the E-government initiatives is the development of the government-to-business (G2B) system, which is an agenda sets to promote a higher service quality between government entities and the business sector. In Jordan, the vision of E-government would be an essential and active participant in the social development and economic with ICT to enable easy access to government services and information. The tender process in Jordan will be assessing based on the capital of the enterprises in order to be tender. However, the main user is the problem of corruption in the selection of tender. This proposal is to develop tender management system for public sector in Jordan, as well as to reduce corruption. The prototype will develop by using C# language , and the research design adopted the general methodology. The evaluation was based on usability testing with the System Usability Scale (SUS) proposed by Brooke. The prototype was assessed by a sample consists of thirty eight respondents. The results have been positive; when the respondents should that they are able to use the system

    An Hybrid, Qos-Aware Discovery of Semantic Web Services Using Constraint Programming

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    Most Semantic Web Services discovery approaches are not well suited when using complex relational, arithmetic and logical expressions, because they are usually based on Description Logics. Moreover, these kind of expressions usually appear when discovery is performed including Quality-of-Service conditions. In this work, we present an hybrid discovery process for Semantic Web Services that takes care of QoS conditions. Our approach splits discovery into stages, using different engines in each one, depending on its search nature. This architecture is extensible and loosely coupled, allowing the addition of discovery engines at will. In order to perform QoS-aware discovery, we propose a stage that uses Constraint Programming, that allows to use complex QoS conditions within discovery queries. Furthermore, it is possible to obtain the optimal offer that fulfills a given demand using this approach.Comisión Interministerial de Ciencia y Tecnología TIN2006-0047

    SLAWS: Towards a Conceptual Architecture for SLA Enforcement

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    Current technologies in Service Oriented Computing (SOC) provide a solid framework to drive the interaction of organizations from a functional point of view. in order to introduce non-functional properties in this scenario, the concept of Service Level Agreement (SLAs) comes into play as a key element. SLAs can be seen as containers of the functional and non-functional properties that both parties (the service consumer and the service provider) agree specifying its rights and obligations during the interaction. However this SLAs represent an additional responsibility for the service provider since it motivates the need of a SLAEnforcement process in its infrastructure. A proper SLAenforcement implies optimized resource usage that meet SLAs established with consumer, making it possible to the provider afford a larger number of customers to maximize its benefits. Current approaches to SLA enforcement are domainspecific approaches and/or based on monolithic platforms (from a SOC point of view).In this paper we propose a conceptual architecture (SLAWs) for SLA enforcement. The main goal of the proposed architecture is to be used as a conceptual framework to build a flexible SLA enforcement layer. This layer could be integrated in a seamless way in the pre-existing provider infrastructure when is based upon the service oriented architecture principles

    Serving people : engineering - a response to aid challenges

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    O título da capa é: Serving people, engineering - a response to aid challenges : Suplly Chain Optimization Project in World Food Program/United NationsEstágio realizado no World Food Programme e orientado pelo Mr. Temmy TanubrataTese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 200

    Combinatorial Auction-based Mechanisms for Composite Web Service Selection

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    Composite service selection presents the opportunity for the rapid development of complex applications using existing web services. It refers to the problem of selecting a set of web services from a large pool of available candidates to logically compose them to achieve value-added composite services. The aim of service selection is to choose the best set of services based on the functional and non-functional (quality related) requirements of a composite service requester. The current service selection approaches mostly assume that web services are offered as single independent entities; there is no possibility for bundling. Moreover, the current research has mainly focused on solving the problem for a single composite service. There is a limited research to date on how the presence of multiple requests for composite services affects the performance of service selection approaches. Addressing these two aspects can significantly enhance the application of composite service selection approaches in the real-world. We develop new approaches for the composite web service selection problem by addressing both the bundling and multiple requests issues. In particular, we propose two mechanisms based on combinatorial auction models, where the provisioning of multiple services are auctioned simultaneously and service providers can bid to offer combinations of web services. We mapped these mechanisms to Integer Linear Programing models and conducted extensive simulations to evaluate them. The results of our experimentation show that bundling can lead to cost reductions compared to when services are offered independently. Moreover, the simultaneous consideration of a set of requests enhances the success rate of the mechanism in allocating services to requests. By considering all composite service requests at the same time, the mechanism achieves more homogenous prices which can be a determining factor for the service requester in choosing the best composite service selection mechanism to deploy
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