This paper investigates the problem of the real-time integration and processing of multimedia metadata collected by a distributed sensor network. The discussed practical problem is the efficiency of the technologies used in creating a Knowledge Base in real-time. Specifically, an approach is proposed for the real-time, rule-based semantic enrichment of lower level context features with higher-level semantics. The distinguishing characteristic is the provision of an intelligent middleware-based architecture on which low level components such as sensors, feature extraction algorithms, data sources, and high level components such as application-specific ontologies can be plugged. Throughout the paper, Priamos, a middleware architecture based on Semantic Web technologies is presented, together with a stress-test of the system’s operation under two test case scenarios: A smart security surveillance application and a smart meeting room application. Performance measurements are conducted and corresponding results are exposed.

This paper presents an evaluation of using the low cost Bluetooth wireless technology, as a localisation technique, fitted in a lightweight approach for providing web-based location aware content through Java enabled handheld devices. This approach separates the positioning system from the content access mechanisms, while being generic and independent to the selection of the localisation technique, i.e., GPS, Bluetooth, etc. A test case application for Bluetooth enabled smart phones demonstrates the capacity of the approach, when combined with Bluetooth localisation, to provide location based content retrieval to the widest possible array of end users, while using their personal mobile devices, without the need to acquire and manage specially built user terminals. Useful results are also extracted for Bluetooth's behaviour, while being used as a localisation technique, with regard to the provided accuracy, usual inquiry time, possible interference from other wireless technologies and imposed hardware requirements.

In this paper we examine the requirements for deploying advanced Location Based Guidance Services in museum and/or exhibition environments, and we propose an architectural approach that copes with these requirements. The proposed architecture provides automatic and on demand audiovisual content retrieval, both on-site and through the Web, to different classes of users. On-site services are provided through Java-enabled devices, which exploit the user's contextual state, mainly defined as visitor location and organization of exhibits. The main distinguishing characteristic of the proposed architecture is that it separates the positioning system from the content access mechanisms, while being generic to the selection of the localization technology and the terminal device characteristics. Furthermore, it is built as an open, modular platform comprising a core of reusable components and interfaces for supporting different types of services and devices, including widespread Java and Bluetooth enabled smart phones, while being able to reuse already existing content structures. A test case of a museum e-guidance application for Bluetooth enabled smart phones is presented.

This paper presents a lightweight approach for providing web-based location aware multimedia content retrieval through Java enabled handheld devices. The main distinguishing characteristic of the proposed approach is that it separates the positioning system from the content access mechanisms, while being generic to the selection of the localization technology, i.e. GPS, Bluetooth, etc. Furthermore, it is built as an open, standards-based, modular architecture comprising a core of reusable components and interfaces for supporting different types of services, through web technologies. On-site services are provided through smart phones, which exploit the user's contextual state, mainly defined as end-user location and organization of points of interest. A test case of a museum e-guidance application for Bluetooth enabled smart phones is presented.

The search of information in heterogeneous systems is always a crucial task. Continuously changing fields of knowledge offer various standards, methods and technology evolvements to satisfy the users’ queries. In this paper we present a catalog based system based upon data collection and harmonization from distributed fields of knowledge that enables the online search and discovery of information from different thematic regions. The key idea is a multiagent platform that enables the connection and interoperability between independent agent entities, oriented however at offering manageability and accuracy. Users can access data and thematic regions not known to them beforehand by the use of the automatic multi-agent system. Our approach is ontologybased, motivated by scenarios of seeking tourist information.

This paper introduces an approach to mapping relational database contents to ontologies. The current effort is motivated by the need of including into the Semantic Web volumes of web data not satisfied by current search engines. A graphical tool is developed in order to ease the mapping procedure and export enhanced ontologies linked to database entities. Moreover, queries using semantic web query languages can be imposed to the database through its connection to an ontology. Using Protege, we were able to map ontology instances into relational databases and retrieve results by semantic web query languages. The key idea is that, instead of storing instances along with the ontology terminology, we can keep them stored in a database and maintain a link to the dataset. Thus, on one hand we achieve smaller size ontologies and on the other hand we can exploit database contents harmonizing the semantic web concept with current wide-spread techniques and popular applications.

In this paper we present E-Museum a system for providing advanced audiovisual guidance services in museums (and exhibitions) to different classes of users. These services include, automatic and on demand audiovisual content retrieval, both onsite and through the Web. On-site services are provided through handheld devices, which exploit the user’s contextual state, mainly defined as visitor location and organization of exhibits. The main distinguishing characteristic of the system is that it is built as an open, modular platform comprising a core of reusable components and interfaces for supporting different types of services and devices.