Spherically symmetric solutions of the λ\lambda-R model

We derive spherically symmetric solutions of the classical \lambda-R model, a minimal, anisotropic modification of general relativity with a preferred foliation and two local degrees of freedom. Starting from a 3 + 1 decomposition of the four-metric in a general spherically symmetric ansatz, we perform a phase space analysis of the reduced model. We show that its constraint algebra is consistent with that of the full \lambda-R model, and also yields a constant mean curvature or maximal slicing condition as a tertiary constraint. Although the solutions contain the standard Schwarzschild geometry for the general relativistic value \lambda = 1 or for vanishing mean extrinsic curvature K, they are in general non-static, incompatible with asymptotic flatness and parametrized not only by a conserved mass. We show by explicit computation that the four-dimensional Ricci scalar of the solutions is in general time-dependent and nonvanishing.Comment: 30 pages, no figure

Protocols versus objects: can models for telecommunications and distributed processing coexist?

This paper identifies two paradigms that influence the design of telematics systems nowadays: the protocol-centred and the object-centred paradigms. Both paradigms have been introduced to cope with interoperability, each in their own way. The coexistence of these paradigms can have an enormous impact on the design of telematics systems. This paper identifies some combined uses of both paradigms and some fundamental research problems related to the coexistence of these paradigm

Historical analysis of spanish competitiveness in the european framework: 19th and 20th centuries

En este artículo se analiza la evolución de la competitividad y el crecimiento económico en España durante los siglos XIX y XX. Una vez definido el concepto de competitividad en relación con otras variables como la productividad, el crecimiento económico, la ventaja comparativa o la competencia internacional, aplicamos este concepto a la experiencia española. El estudio incluye la evolución del Producto Interior Bruto español en función de su convergencia o divergencia, la contribución histórica del trabajo, el capital y la productividad total de los factores en el desarrollo español, las contribuciones del marco institucional, y la evolución de la competitividad en las regiones, clusters y empresas españolas. Entre otras conclusiones, el artículo destaca la progresiva reducción del proteccionismo y el intervencionismo económico desde 1959, políticas que habían sido introducidas a finales del siglo XIX, y cuya reforma y eliminación permitieron un intenso crecimiento económico y un proceso de convergencia. Pero la economía española todavía mantiene algunas deficiencias institucionales que reducen el potencial de crecimiento económico y afecta a la competitividad y el espíritu empresarial en España.This article analyzes the evolution of Spanish competitiveness and economic growth during the 19th and 20th century. After defining the concept of competitiveness in relation with other notions like productivity, economic growth, comparative advantage, or international competition, we apply this concept to the Spanish experience. The study includes the evolution of the Spanish Gross Domestic Product in terms of its convergence and divergence, the historical contribution of labor, capital, and total factor productivity on Spanish development, the institutional contributions to growth, and the evolution of competitiveness in Spanish regions, clusters and companies. Among other conclusions, the article emphasizes that, since 1959, the progressive reduction of protectionism and intense public regulations, introduced at the end of the 19th century, allowed an intense economic growth and convergence process. But the Spanish economy still maintains some institutional shortcomings that reduce its potential future growth and affect its competitiveness and entrepreneurship

An Analysis of Service Ontologies

Services are increasingly shaping the world’s economic activity. Service provision and consumption have been profiting from advances in ICT, but the decentralization and heterogeneity of the involved service entities still pose engineering challenges. One of these challenges is to achieve semantic interoperability among these autonomous entities. Semantic web technology aims at addressing this challenge on a large scale, and has matured over the last years. This is evident from the various efforts reported in the literature in which service knowledge is represented in terms of ontologies developed either in individual research projects or in standardization bodies. This paper aims at analyzing the most relevant service ontologies available today for their suitability to cope with the service semantic interoperability challenge. We take the vision of the Internet of Services (IoS) as our motivation to identify the requirements for service ontologies. We adopt a formal approach to ontology design and evaluation in our analysis. We start by defining informal competency questions derived from a motivating scenario, and we identify relevant concepts and properties in service ontologies that match the formal ontological representation of these questions. We analyze the service ontologies with our concepts and questions, so that each ontology is positioned and evaluated according to its utility. The gaps we identify as the result of our analysis provide an indication of open challenges and future work

Design of a shared whiteboard component for multimedia conferencing

This paper reports on the development of a framework for multimedia applications in the domain of tele-education. The paper focuses on the protocol design of a specific component of the framework, namely a shared whiteboard application. The relationship of this component with other components of the framework is also discussed. A salient feature of the framework is that it uses an advanced ATM-based network service. The design of the shared whiteboard component is considered representative for the design as a whole, and is used to illustrate how a flexible protocol architecture utilizing innovative network functions and satisfying demanding user requirements can be developed

Towards a Unifying Process Framework for Services Knowledge Management

Activities concerned with the design, planning and execution of services are becoming increasingly complex. This is due to the involvement of many different stakeholders, the complexity of the service systems themselves, and the dynamic nature of their organizational and ICT environments. Service knowledge management helps share and reuse relevant knowledge among the different stakeholders, and therefore emerges as a critical factor to perform service activities with required efficiency and quality. Recent advances in knowledge management provide promising opportunities to support individual service activities within a single domain. Yet, sharing knowledge throughout the service life-cycle and across service domains is still very challenging. The source of service knowledge, its usage, update frequency, encoding and associated stakeholders may vary depending upon the service activity and the service domain. Based on a critical analysis of currently proposed frameworks, we argue that a process framework approach is beneficial for service knowledge management. To support our claim, we offer an abstract template and a typical service life-cycle that can be adopted to integrate heterogeneous service knowledge from diverse sources

Supporting Dynamic Service Composition at Runtime based on End-user Requirements

Network-based software application services are receiving a lot of attention in recent years, as observed in developments as Internet of Services, Software as a Service and Cloud Computing. A service-oriented computing ecosystem is being created where the end-user is having an increasingly more active role in the service creation process. However, supporting end-users in the creation process, at runtime, is a difficult undertaking. Users have different requirements and preferences towards application services, use services in different situations and expect highly abstract mechanisms in the creation process. Furthermore, there are different types of end-users: some can deliver more detailed requirements or can be provided with more advanced request interface, while others can not. To tackle these issues and provide end-users with personalised service delivery, we claim that runtime automated service composition mechanisms are required. In this paper we present the DynamiCoS framework, which aims at supporting the different phases required to provide end-users with automatic service discovery, selection and composition process. In this paper we also present the developed prototype and its evaluation

What makes industries believe in formal methods

The introduction of formal methods in the design and development departments of an industrial company has far reaching and long lasting consequences. In fact it changes the whole environment of methods, tools and skills that determine the design culture of that company. A decision to replace current design practice by formal methods, therefore, appears a vital one and is not lightly taken. The past has shown that efforts to introduce formal methods in industry has faced a lot of controversy and opposition at various hierarchical levels in companies, resulting in a marginal spread of such methods. This paper revisits the requirements for formal description techniques and identifies some critical success and inhibiting factors associated with the introduction of formal methods in the industrial practice. One of the inhibiting factors is the often encountered lack of appropriateness of the formal model to express and manipulate the design concerns that determine the world of the engineer. This factor motivated our research in the area of architectural and implementation design concepts. The last two sections of this paper report on some results of this research