42 research outputs found
A Model of User Preferences for Semantic Services Discovery and Ranking
Current proposals on Semantic Web Services discovery and
ranking are based on user preferences descriptions that often come with
insufficient expressiveness, consequently making more difficult or even
preventing the description of complex user desires. There is a lack of a
general and comprehensive preference model, so discovery and ranking
proposals have to provide ad hoc preference descriptions whose expressiveness
depends on the facilities provided by the corresponding technique,
resulting in user preferences that are tightly coupled with the
underlying formalism being used by each concrete solution. In order to
overcome these problems, in this paper an abstract and sufficiently expressive
model for defining preferences is presented, so that they may be
described in an intuitively and user-friendly manner. The proposed model
is based on a well-known query preference model from database systems,
which provides highly expressive constructors to describe and compose
user preferences semantically. Furthermore, the presented proposal is independent
from the concrete discovery and ranking engines selected, and
may be used to extend current Semantic Web Service frameworks, such
as wsmo, sawsdl, or owl-s. In this paper, the presented model is also
validated against a complex discovery and ranking scenario, and a concrete
implementation of the model in wsmo is outlined.ComisiĂłn Interministerial de Ciencia y TecnologĂa TIN2006-00472ComisiĂłn Interministerial de Ciencia y TecnologĂa TIN2009-07366Junta de AndalucĂa TIC-253
Quality-aware model-driven service engineering
Service engineering and service-oriented architecture as an integration and platform technology is a recent approach to software systems integration. Quality aspects
ranging from interoperability to maintainability to performance are of central importance for the integration of heterogeneous, distributed service-based systems. Architecture models can substantially influence quality attributes of the implemented software systems. Besides the benefits of explicit architectures on maintainability and reuse, architectural constraints such as styles, reference architectures and architectural patterns can influence observable software properties such as performance. Empirical performance evaluation is a process of measuring and evaluating the performance of implemented software. We present an approach for addressing the quality of services and service-based systems at the model-level in the context of model-driven service engineering. The focus on architecture-level models is a consequence of the black-box
character of services
A Requirement-centric Approach to Web Service Modeling, Discovery, and Selection
Service-Oriented Computing (SOC) has gained considerable popularity for implementing Service-Based Applications (SBAs) in a flexible\ud
and effective manner. The basic idea of SOC is to understand users'\ud
requirements for SBAs first, and then discover and select relevant\ud
services (i.e., that fit closely functional requirements) and offer\ud
a high Quality of Service (QoS). Understanding users requirements\ud
is already achieved by existing requirement engineering approaches\ud
(e.g., TROPOS, KAOS, and MAP) which model SBAs in a requirement-driven\ud
manner. However, discovering and selecting relevant and high QoS\ud
services are still challenging tasks that require time and effort\ud
due to the increasing number of available Web services. In this paper,\ud
we propose a requirement-centric approach which allows: (i) modeling\ud
users requirements for SBAs with the MAP formalism and specifying\ud
required services using an Intentional Service Model (ISM); (ii)\ud
discovering services by querying the Web service search engine Service-Finder\ud
and using keywords extracted from the specifications provided by\ud
the ISM; and(iii) selecting automatically relevant and high QoS services\ud
by applying Formal Concept Analysis (FCA). We validate our approach\ud
by performing experiments on an e-books application. The experimental\ud
results show that our approach allows the selection of relevant and\ud
high QoS services with a high accuracy (the average precision is\ud
89.41%) and efficiency (the average recall is 95.43%)
Context-Aware Service Selection with Uncertain Context Information
The current evolution of Service-Oriented Computing in ubiquitous systems
is leading to the development of context-aware services. These are services
whose description is enriched with context information related to the service execution
environment and adaptation capabilities. This information is often used for discovery
and adaptation purposes. However, in real-life systems context information
is naturally dynamic, uncertain and incomplete, which represents an important issue
when comparing service description and user requirements. Uncertainty of context
information may lead to an inexact match between provided and required service
capabilities, and consequently to the non-selection of services. In order to handle
uncertain and incomplete context information, we propose a mechanism inspired
by graph-comparison for matching contextual service descriptions using similarity
measures that allow inexact matching. Service description and requirements are
compared using two kinds of similarity measures: local measures, which compare
individually required and provided properties, and global measures, which take into
account the context description as a whole. We show how the proposed mechanism
is integrated in MUSIC, an existing adaptation middleware, and how it enables more
optimal adaptation decision making
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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
An extended ontology-based context model and manipulation calculus for dynamic web service processes
Services are oered in an execution context that is determined by how a provider provisions the service and how the user consumes it. The need for more exibility requires the provisioning and consumption aspects to be addressed at runtime. We propose an ontology-based context model providing a framework for service provisioning and consumption aspects and techniques for managing context constraints for Web service processes where dynamic context concerns can be monitored and validated at service process run-time.
We discuss the contextualization of dynamically relevant
aspects of Web service processes as our main goal, i.e. capture aspects in an extended context model. The technical contributions of this paper are a context model ontology for dynamic service contexts and an operator calculus for integrated and coherent context manipulation, composition and reasoning. The context model ontology formalizes dynamic aspects of Web services and facilitates reasoning. We present the context ontology in terms of four core dimensions - functional, QoS, domain and platform - which are internally interconnected
Flexible workflows to support transactional service composition in mobile environments
Service oriented computing provides suitable means to technically support
distributed collaboration of heterogeneous devices, for example those present
in mobile environments. E.g., many applications are built on composite Web-
Services. However, when executing these applications in dynamic environments,
failures of participating entities have to be optimistically coped with, in
order to avoid inconsistent system states and thereby provide suitable
correctness guarantees. Transactional coordination for services so far lacks
the possibility to adapt failure handling to the current execution context,
e.g. dynamically bound services at runtime. In this paper, we employ
transactional service properties to ensure reliable, i.e., correct execution
of workflows by still respecting the autonomy of participants. We propose
algorithms to verifiy and alter the structure of the composition at runtime,
thus adapting the control flow to the current execution context to ensure
correct execution
DCC Digital Curation Manual: Instalment on Ontologies
Instalment on the role of ontologies within the digital curation life-cycle. Describes the increasingly important role of ontologies for digital curation, some practical applications, the topicâs place within the OAIS reference model, and advice on developing institution-specific selection frameworks