Dimitrios A. Kateros

Model-driven development of composite context-aware web applications

Context-awareness constitutes an essential aspect of services, especially when interaction with end-users is involved. In this paper a solution for the context-aware development of web applications consisting of web services is presented. The methodology proposes a model based approach and advocates in favour of a complete separation of the web application functionality from the context adaptation at all development phases (analysis, design, implementation). In essence, context adaptation takes place on top of and is transparent to the web application business functionality. Starting from UML diagrams of independent web services and respective UML context models, our approach can produce a functional composite context-aware application. At execution level this independence is maintained through an adaptation framework based on message interception.

Service Composition: State of the art and future challenges

Service discovery and service composition constitute challenging tasks of service provisioning. Service composition is especially gaining on importance, as it can produce new composite services with features not present in the individual services. Many methods have been proposed over the years to address these issues. Simple Mobile Services (SMS) is a project aiming at creating innovative tools that will introduce a new class of mobile services enabling individuals and small businesses to become service providers. In this paper an attempt is made to present an overview of all existing techniques on service composition and examine them in the context of SMS. The enumeration of the techniques is complete and focuses mostly on recent approaches. Moreover, service composition is discussed under the prism of mass service provisioning by mobile operators where some techniques currently seem to be more suitable than others.

Architecture for provision of context-aware web applications based on web services

Mobile and pervasive computing is gaining significant importance in the latest years. Context-awareness constitutes an essential aspect - almost a requirement - of mobile services in these environments. In this paper, we propose an architecture that supports the development and provision of context-aware services. The described approach provides means for the context adaptation of software components exposed as Web services independently of their specific implementation allowing for added flexibility concerning the adaptation itself or whether it is performed at all. As the service logic is clearly separated from the context adaptation, the same principle can be applied to composite Web services. Specifically, we show that different services and context sources can be combined to provide a Web application separating completely the application logic from the context adaptation. Context plugins loaded on runtime are responsible for invoking the right context sources to retrieve the necessary context information and complete the service adaptation to context.

A Methodology for Model-Driven Web Application Composition

Web application composition can greatly benefit from the utilization of existing frameworks and reusable components, in order to reduce development effort. Frameworks implementing the model-view-controller architectural pattern standardize the development process to a great extent, while business layer components may consist of consumers of existing Web services. On this line of thought a Web application can be seen as a composition of Web services around a user interface flow. In this paper, an approach for the application of model-driven techniques for the automation of the development of such a Web application is presented. Specifically, we present a methodology for the modeling of the application using UML state transition and class diagrams and the generation of the appropriate source code and configuration files. The appropriate UML profiles to assist the service design are defined and the final transformation is performed exploiting model parsing tools.

Architecture for reliable service discovery and delivery in manets based on power management employing slp extensions

Limited energy resources and mobility issues affect the topology of ad hoc networks and introduce difficulties in service discovery. The high possibility of a link breakdown due to low energy supplies in a ubiquitous computing environment, such as a mobile ad hoc network (MANET), raises service-provider selection issues with regard to achieving the best possible service reliability. Every node requiring a specific service must choose a provider under certain criteria. This article provides an overview of standardized service-discovery and delivery solutions. In addition, a novel architecture is proposed which provides the ability to select a service provider by taking into account metrics such as the power supplies of the service provider and concomitant path towards the destination. The proposed algorithm is decentralized and based on service location protocol version 2 (SLPvZ) extensions

DVB-T Network Planning: A Case Study for Greece

Terrestrial digital video broadcasting (DVB-T) network planning is the main interest of this article, along with a case study for Greece. The basic principles and the guidelines of the DVB-T planning process are presented, in conjunction with their application to the establishment of the Greek DVB-T allotment plan. The procedures described in this article were followed by the authors during the International Telecommunication Union (ITU) DVB-T planning project that concluded with the ITUs Regional Radiocommunication Conference 2006 (RRC-06), and the Geneva (GE-06) frequency plan for terrestrial digital radio broadcasting.

Model-driven development of composite web applications

As the number of available web services increases, the development of web applications that integrate existing web services becomes more and more popular. This class of web applications can be seen as the composition of web services around a user interface flow. In this paper, the application of model-driven techniques for the development of such user-centric web applications is presented. An approach for the modeling of the application using UML class and state transition diagrams and the transformation to appropriate platform specific code is presented. The service design is based on the introduced UML profiles, whereas on code level frameworks implementing the Model-View-Controller architectural pattern are targeted.

An Algorithm for the Frequency Assignment Problem in the Case of DVB-T Allotments

In this paper, we investigate the allocation of frequency channels to DVB-T allotments for frequency Bands IV/V (UHF). The problem is modeled with a constraint graph represented by an interference matrix. The aim is to optimize the spectrum usage, so that the maximum number of possible channels is assigned to each allotment area. The problem is a variation of the Frequency Assignment Problem (FAP). We have developed an algorithm that uses metaheuristic techniques, in order to obtain possible solutions. Three versions of the algorithm, a Tabu Search, a Simulated Annealing, and a Genetic Algorithm version, are evaluated. We present and discuss comparative results of these versions for generated networks, as well as for real allotment networks that are included in the GE06 digital frequency plan produced by ITU during the RRC-06 conference.

Enabling the deployment of mobile services for end-users: the SMS approach

Service provision in mobile environments is nowadays moving toward easiness and openness. The end-user’s role in this procedure can be supported through platforms that encourage user’s participation. This is critical toward the success of community-oriented service platforms that rely on end-user-generated content. The current paper describes an approach toward the participation of non-expert users in the development, deployment and provision of mobile services referred as Simple Mobile Services. The solution has been developed in the framework of the SMS project. The overall management is supported by the service-oriented structure of the SMS system infrastructure. The service authoring is facilitated through the SMS Authoring Wizard giving users the opportunity to create and deploy services inspecting them instantly on their mobile terminals.