Vassileios Tsetsos

Semantically enriched navigation for indoor environments

Location-based mobile services have been in use, and studied, for a long time. With the proliferation of wireless networking technologies, users are mostly interested in advanced services that render the surrounding environment (i.e., the building) highly intelligent and significantly facilitate their activities. In this paper our focus is on indoor navigation, one of the most important location services. Existing approaches for indoor navigation are driven by geometric information and neglect important aspects, such as the semantics of space and user capabilities and context. The derived applications are not intelligent enough to catalytically contribute to the pervasive computing vision. In this paper, a novel navigation mechanism is introduced. Such navigation scheme is enriched with user profiles and the adoption of an ontological framework. These enhancements introduce a series of technical challenges that are extensively discussed throughout the paper.

Sensation: a middleware integration platform for pervasive applications in wireless sensor networks

In this paper we focus on the issue of application development for wireless sensor networks (WSN). Currently, such networks are extensively used in various business domains. However, their highly customized operating systems and application middleware render the application development for multiple WSNs rather cumbersome. Applications based on multiple WSNs are typical in the emerging pervasive computing paradigm adopted in numerous domains (e.g., telemedicine). A WSN can be considered as a source of information similarly to a database. Motivated by the layered driver approach introduced in the ODBC/JDBC frameworks, we propose a middleware integration architecture. Our architecture presents a unified and developer-friendly interface and abstract data model towards the application. Such interface conceals the peculiarities of the underlying WSNs as their coordination and data retrieval software is integrated in the lower layer of the proposed middleware framework. We present the design of the discussed architecture that is based on open standards like XML.

On the Evaluation of Semantic Web Service Matchmaking Systems

Semantic Web services are generally considered as the evolution of conventional Web services. Semantic information included in the service descriptions enables the development of advanced matchmaking schemes, capable of assigning degrees of match to the discovered services. In this paper, we address issues related to the evaluation of the retrieval effectiveness of semantic matchmaking systems. Our main position is that conventional evaluation schemes do not fully capture the added value of service semantics nor do they take into account the assigned degrees of match, supported by the majority of discovery engines. Through some preliminary experiments, we show that a generalization of the evaluation process based on fuzzy set theory techniques can lead to more accurate and meaningful evaluation results

A human-centered semantic navigation system for indoor environments

In this paper we discuss the very important issue of indoor location services. Location services have been in use, and studied, for a long time in mobile networks. With the proliferation of wireless networking technologies, users are mostly interested in advanced services that render the surrounding environment (i.e., the building) highly intelligent and significantly facilitate user activities (pervasive computing paradigm). Our focus is on navigation, one of the most important location services. Existing approaches for indoor navigation are driven by geometric information and neglect important aspects like the semantics of points/areas and user preferences. The derived applications are not intelligent enough to catalytically contribute to the pervasive computing vision. In this paper, a novel navigation mechanism is introduced. Such navigation scheme is enriched with user profiles and the adoption of an ontological framework. These enhancements introduce a series of technical challenges that are extensively discussed throughout the paper.

Commercial wireless sensor networks: technical and business issues

In this paper we study the opportunities of commercial exploitation of applications based on sensor networks. Such applications are quite famous nowadays in many different domains of everyday life (e.g., health monitoring, traffic monitoring). We introduce a new business model for sensor based services. Such business model involves entities like the mobile network operator and capitalizes on existing standards for application service providers (e.g., the OSA/Parlay standard). We also present the required technical framework that would facilitate the introduction and rapid adoption of the proposed business schemes.

Performance evaluation of a self-evolving trust building framework

A self-evolving reputation scheme for trust establishment in distributed peer networks is presented and evaluated. The framework, called ad-hoc trust framework (ATF), incorporates subjective behavior of end-users, direct observations of behaviors, recommendations, and history of evidences to assess the trustworthiness of peer entities. It considers several idiosyncrasies of the wireless self-organized networks, such as lack of computational resources. ATF is associated with a generic model for the evaluation of the trustworthiness of adjacent or distant nodes. It relies on a sophisticated reputation method, called trustspan, to contact only trusted peers for recommendations, and, thus, it minimizes communication costs for trust building, accelerating the trust evolution process. To evaluate the performance of the ATF framework we have deployed a large number of simulation scenarios. The performance assessment results show that ATF achieves to rapidly identify selfish nodes with high accuracy, and with relatively low communication costs.

MNISIKLIS:Indoor Location Based Services for All

MNISIKLIS is an integrated system aiming to provide universal, indoor locationbased services focusing on navigation. This paper presents the overall MNISIKLIS architecture and certain implementation details. In the context of the Design for All approach, the system targets to the support of several types of users, including persons with disabilities as well as elderly, by exploiting multimodal interaction. Moreover, the system implements effi cient path fi nding algorithms and provides advanced user experience through highly personalized services. MNISIKLIS adopts Semantic Web technologies (e.g., ontologies and reasoning methods) for representing an d managing application models. Furthermore, MNISIKLIS exploits modern positioning techniques in order to achieve high quality positioning. The paper discusses the algorithms and the models that accommodate the services provided by the system. Additionally, an analysis of the positioning subsystem, the user interaction subsystem and the peripheral infrastructure is given. Hence, a new paradigm in the area of location-based systems is presented.

A scheduling framework for enterprise services

Application-level scheduling is a common process in the enterprise domain, but in order to be productive it should be time-effective, interoperable and reliable. In this paper we present the design and implementation aspects of a modular scheduling solution, which aims to fulfill the above-mentioned requirements. The proposed solution constitutes an integral part of an existing service provisioning platform targeted to the location based services (LBS) domain; however application to other service-oriented architectures is also possible. A careful design process is followed in order to identify the schedulers functional subsystems and the relationships between them. The implementation is based on the J2EE framework, thus guaranteeing independence from underlying technologies and applicability in enterprise environments. The high quality and scalability of the scheduler is also validated through an intensive performance analysis.

Busfinder: A Personalized Multimodal Transportation Guide with Dynamic Routing

Multimodal routing services with public transportation are already present in many large cities across the globe. In this paper we describe a mobile guide that goes beyond existing solutions, mainly due to its service personalization and its dynamic routing algorithm. Personalization is based on knowledge engineering principles and Semantic Web technologies. The dynamic routing algorithm is based on short term history and estimators and supports cities with pre-installed fleet management systems in the public transport means.

Trust management issues for ad hoc and self-organized networks

Self-organized and ad hoc communications have many fundamental principles in common and also face similar problems in the domains of security and Quality of Service. Trust management, although still in its first steps, seems capable of dealing with such problems. In this paper we present an integrated trust management framework for self-organized networks. In addition, starting from our experience with the presented framework, we indicate and discuss important research challenges (among them interoperability and integration issues) for the future evolution of the trust-based autonomic computing paradigm. We argue that ontologies can address many of these issues through the semantics they convey.