Evangelos Sakkopoulos

Techniques to support Web Service selection and consumption with QoS characteristics

This work proposes a Web Service (WS) discovery model in which the functional and non-functional requirements are taken into account during service discovery. The proposed infrastructure includes a set of services and tools to support an integrated WS discovery and selection solution. A mechanism is introduced that supports three different functional policies. It is able to take advantage of quality information located into a Web Service description language description file that might be located in a proprietary universal description, discovery and integration registry server or in an independent URL. Moreover, it implements a database supported WS intermediary (Broker) that it is also possible to store quality of service (QoS) information for WSs. A selection module is also presented that delivers the WS that maximizes the value of QoS characteristics among others with the same functionality. An experimental prototype is presented and evaluated in the scenario of air ticket issuing WS selection.

Category ranking for personalized search

Despite the effectiveness of search engines, the persistently increasing amount of web data continuously obscures the search task. Efforts have thus concentrated on personalized search that takes account of user preferences. A new concept is introduced towards this direction; search based on ranking of local set of categories that comprise a user search profile. New algorithms are presented that utilize web page categories to personalize search results. Series of user-based experiments show that the proposed solutions are efficient. Finally, we extend the application of our techniques in the design of topic-focused crawlers, which can be considered an alternative personalized search.

Efficient and adaptive discovery techniques of Web Services handling large data sets

Attempts have been made concerning the search and finding of a Web Service based on keywords and descriptions. However, no work has been done concerning the efficient selection of the appropriate Web Service instance in terms of quality and performance factors at the moment of the Web Service consumption attempt. Such factors may include execution time and response time. The proposed approach adaptively selects the most efficient WS among possible different alternatives with real-time, optimized and countable factors-parameters. Implementation issues and case study experiments are presented along with the corresponding results. Additionally, an optimal selection algorithm for series of Web Services requests is proposed. Finally, conclusions and future steps are discussed.

Semantic Web and Knowledge Management for the health domain: state of the art and challenges for the Seventh Framework Programme (FP7) of the European Union (2007-2013)

Information Systems in the context of the health domain play a critical role. The evolution of the semantic web and knowledge management technologies in the last years set a new context for the exploitation of patient-centric strategies based on well-defined semantics and knowledge. In this paper we have two critical objectives. On the one hand to exploit the state of the art on Semantic Web and Knowledge Management (KM) approaches in the context of the health domain and on the other hand to underline the key challenges within the FP7 framework of the European Union for customised and personalised health services.

Health Internet of Things: Metrics and methods for efficient data transfer

Abstract The rapid development of modern Information and Communication Technologies (ICTs) in recent years and their introduction into people’s daily lives worldwide, has led to new circumstances at all levels of the social environment. In health care in particular, sensors and data links offer potential for constant monitoring of patient’s symptoms and needs, in real time, enabling physicians to diagnose and monitor health problems wherever the patient is, either at home or outdoors. However, the use of Internet of Things concepts in the health domain does not come without extra data and therefore a data transfer cost overheads. To deal with these overheads, novel metrics, and methods are introduced in an attempt to maximize the capabilities and widen acceptance/usage provided by the Internet of Things. Without losing its generality, the method discussed is experimentally evaluated in the paradigm of the Health domain. The focus is on the need for an overview of available data formats and transmission methods and selection of the optimal combination, which can result to reduction/minimization of costs. An analytic methodology is presented backed with theoretical metrics and evaluated experimentally.

Dynamic Web Service discovery architecture based on a novel peer based overlay network

Service Oriented Computing and its most famous implementation technology Web Services (WS) are becoming an important enabler of networked business models. Discovery mechanisms are a critical factor to the overall utility of Web Services. So far, discovery mechanisms based on the UDDI standard rely on many centralized and area-specific directories, which poses information stress problems such as performance bottlenecks and fault tolerance. In this context, decentralized approaches based on Peer to Peer overlay networks have been proposed by many researchers as a solution. In this paper, we propose a new structured P2P overlay network infrastructure designed for Web Services Discovery. We present theoretical analysis backed up by experimental results, showing that the proposed solution outperforms popular decentralized infrastructures for web discovery, Chord (and some of its successors), BATON (and its successor) and Skip-Graphs.

Web Service discovery based on Quality of Service

Late developments in Web Service discovery approaches mainly focus on the incorporation of the QoS concept in the selection process. In this paper, we present a generalized design and implementation of a QoS enabled Web Service discovery mechanism. We describe a mechanism extending the propositions of [1] in a generalized environment that consists of dynamic groups/ categories of different Web Services. A UDDI search wrapper is introduced to facilitate the traditional WS discovery by taking into account QoS characteristics in transparent way. Our aim is the combination of the classic Web Service discovery, at design or execution time, with the benefit of QoS characteristics without affecting the existing UDDI search facilities. To evaluate the functionality, feasibility and effectiveness of the mechanism proposed, a number of experimental applications have been developed. All applications have been available for evaluation online in laboratory.

Efficient web-based open and distance learning services

Abstract In this paper, we present data management issues faced during the design and development of an open distance learning system for the University of Patras, Greece. In order to handle data efficiently, as required in a web tele-training application, for each type of information maintained, different strategies must be deployed according to their behaviour and structure. The diversity and complexity of data, the network aspect of the application and web deficiencies impose an architecture design incorporating a plethora of technologies and tools that must be integrated in such a fashion that they efficiently organise these data preserving their relationships. This presents a software engineering challenge requiring coherence of solutions at all levels: structures, consistency, security, models, and protocols. The paper presents the data components of an open and distance learning (ODL) system that access the information stored in a database and the file system, their underlying technology, their interaction with the network services, and features regarding the ways they address issues faced in an open vendor-independent distance learning environment and outlines the systems overall architecture. In addition, this paper presents the architecture, the design and the services of a network-based information system that supports open and distance learning activities. The open and distance learning information system (ODLIS) offers synchronous and asynchronous distance learning and management of information system (MIS) services to support the educational procedure. The ODLIS is a web-based application, which runs over the Internet using real time protocols.

easyHealthApps: e-Health Apps Dynamic Generation for Smartphones & Tablets

Mobile phones and especially smartphones have been embraced by a rapidly increasing number of people worldwide and this trend is expected to evolve even more in the years to come. There are numerous smartphone Apps that record critical medical data in an effort to solve a particular health issue each time. We studied such applications and not surprisingly, we have found that development and design effort is often repeated. Software patterns have been detected to exist, however re-usability has not been enforced. This leads to lost programming manpower and to increased probability of repeating bugs in Apps. Moreover, at the moment smartphone e-Health Apps demand time, effort and costs for development. Unfortunately even simple data recording Apps are practically impossible to be produced by multiple health domain users who are not developers. In this work, we propose, design and implement a simple and integrated solution which gives healthcare professionals and researchers the ability to create their own data intensive smartphone applications, independent of the desired healthcare domain. The proposed approach applies efficient software techniques that hide development from the users and enable App creation through a simple Web User Interface. The Apps produced are in native format and it is possible to dynamically receive m-Health business logic and the chosen UI. Evaluation of the proposed solution has shown that the generated Apps are functionally and UI equivalent to human-coded Apps according to a number of comparison parameters. Furthermore, e-Health professionals show particular interest in developing Apps on their own for a particular domain they focus on.

A novel distributed P2P simulator architecture: D-P2P-sim

In this paper we introduce a novel distributed simulation environment with GUI for P2P simulations (D-P2P-Sim). The key aim is to provide the appropriate integrated set of tools in a single software solution to evaluate the performance of various protocols. The basic architecture of the distributed P2P simulator is based on a multi-threading, asynchronous, message passing and distributed environment with graphical user interface to facilitate ease of use by both researchers and programmers.