Catálogo de publicaciones - libros

With the increasing availability of Web services and adoption of services oriented paradigm, there is a growing need to dynamically compose services for realizing complex user tasks. While service composition is itself an important problem, a key issue is also how to support users in selecting the most appropriate compositions of services to fulfill a task. In existing dynamic services selection approaches, combinations of services are repeatedly discovered (e.g., using ontology-based matching techniques) and selected by users whenever needed. To improve their effectiveness, we propose a new technique that provides an efficient access to what is named a “task memory”. A task memory is used to provide users with a context-aware service selection by recommending combinations of services that are most appropriate in a given context. A task memory is formed using the service composition history and their metadata. We present an incremental approach for building the task memory in which we monitor how users use and rank the services. The continuous updates of the task memory over time will result in more fine-tuned recommendations for composite services.

In the last years both industry and academia have shown a great interest in ensuring consistent cooperation for business-critical services, with contractually agreed levels of Quality of Service. Service Level Agreement specifications as well as techniques for their evaluation are nowadays irremissible assets. This paper presents Puppet (Pick UP Performance Evaluation Test-bed), an approach and a tool for the automatic generation of test-beds to empirically evaluate the QoS features of a Web Service under development. Specifically, the generation exploits the information about the coordinating scenario (be it choreography or orchestration), the service description (WSDL) and the specification of the agreements (WS-Agreement).

Business to business integration has recently been performed by employing Web service environments. Moreover, such environments are being provided by major players on the technology markets. Those environments are based on open specifications for transaction coordination. When a failure in such an environment occurs, a compensation can be initiated to recover from the failure. However, current environments have only limited capabilities for compensations, and are usually based on backward recovery. In this paper, we introduce an engineering approach and an environment to deal with advanced compensations based on forward recovery principles. We extend the existing Web service transaction coordination architecture and infrastructure in order to support flexible compensation operations. A contract-based approach is being used, which allows the specification of permitted compensations at runtime. We introduce the and components which allow us to separate the compensation logic from the coordination logic. In this way, we can easily plug in or plug out different compensation strategies based on a specification language defined on top of basic compensation activities and complex compensation types. Experiments with our approach and environment show that such an approach to compensation is feasible and beneficial.

We describe the CAWE framework for the management of context-aware workflow systems, based on Web Services. The framework is based on a hierarchical workflow representation supporting a synthetic and extensible specification of context-sensitive workflows, which can be executed by standard workflow engines. We have exploited the CAWE framework to develop a prototype application handling a medical guideline specifying the activities to be performed in order to monitor patients treated with blood thinners.

In service-oriented computing (SOC), services are designed not just for a dedicated client but for a family of potential clients. For services to be generic and serviceable to different clients, service variability among the clients must be analyzed and modeled into service components. is an architectural framework for service integration, but it does not provide effective adaptation mechanisms. Hence, it is desirable to devise techniques to adapt services on ESB for specific service requests. In this paper, we identify four types of service variability, and we present methods to adapt services provided on ESB. These methods can be practically applied in designing highly adaptable services on ESB.

Initially, web development methods focused on the generation of read-only web applications for browsing the data stored in relational database systems. Lately, many have evolved to include content-modification functionalities. As a consequence, we believe that existing quality properties for web model designs must be complemented with new property definitions. In particular, we propose two new quality properties that take the relationship between navigation models and the related data models into account. The properties check if navigation models include all necessary content-modification operations and whether all possible navigation paths modify the underlying data in a consistent way. In this paper, we show how to determine if a navigation model verifies both properties and also how to, given a data model, automatically generate a preliminary navigation model satisfying them.

WE practices lack an impact on industry, partly due to a WE field that is not quality-aware. In fact, it is difficult to find WE methodologies that pay explicit attention to quality aspects. However, the use of a systematic process that includes quality concerns from the earliest stages of development can contribute to easing the building up of quality-guaranteed Web applications without drastically increasing development costs and time-to-market. In this kind of process, quality issues should be taken into account while developing each outgoing artifact, from the requirements model to the final application. . Also, quality models should be defined to evaluate the quality of intermediate WE artifacts and how it contributes to improving the quality of the deployed application. In order to tackle its construction while avoiding some of the most common problems that existing quality models suffer from, in this paper we propose a number of WE quality models to address the idiosyncrasies of the different stakeholders and WE software artifacts involved. Additionally, we propose that these WE quality models are supported by an ontology-based WE measurement meta-model that provides a set of concepts with clear semantics and relationships. This WE Quality Metamodel is one of the main contributions of this paper. Furthermore, we provide an example that illustrates how such a metamodel may drive the definition of a particular WE quality model.

The objective of this paper is to describe the use of a probabilistic approach to Web effort estimation by means of a Bayesian Network. A Bayesian Network is a model that embodies existing knowledge of a complex domain in a way that supports reasoning with uncertainty. Given that the causal system relative to Web effort estimation has an inherently uncertain nature the use of Bayesian model seemed a reasonable choice. We used a cross-company data set of 150 industrial Web projects volunteered from Web companies worldwide, which are part of the Tukutuku database. Results showed that the effort estimates obtained using a Bayesian Network were sound and significantly superior to the prediction based on two benchmark models, using the mean and median effort respectively.

Servlet cache can effectively improve the throughput and reduce response time experienced by customers in servlet container. An essential issue of servlet cache is cache replacement. Traditional solutions such as LRU, LFU and GDSF only concern some intrinsic factors of cache objects regardless of associations among cached objects. For higher performance, some approaches are proposed to utilize these associations to predict customer visit behaviors, but they are still restricted by first-order Markov model and lead to inaccurate predication. In this paper, we describe associations among servlets as sequential patterns and compose them into pattern graphs, which eliminates the limitation of Markov model and achieve more accurate predictions. At last, we propose a discovery algorithm to generate pattern graphs and two predictive probability functions for cache replacement based on pattern graphs. Our evaluation shows that this approach can get higher cache hit ratio and effectively improve the performance of servlet container.

, a scientific literature search engine that focuses on documents in the computer science and information science domains, suffers from scalability issue on the number of requests and the size of indexed documents, which increased dramatically over the years. CiteSeer is an effort to re-architect the search engine. In this paper, we present our initial design of a framework for caching query results, indices, and documents. This design is based on analysis of logged workload in CiteSeer. Our experiments based on mock client requests that simulate actual user behaviors confirm that our approach works well in enhancing system performances.