This paper presents a distributed client-server architecture for the personalized delivery of textual news content to mobile users. The user profile consists of two separate models, that is, the long-term interests are stored in a skeleton profile on the server and the short-term interests in a detailed profile in the handset. The user profile enables a high-level filtering of available news content on the server, followed by matching of detailed user preferences in the handset. The highest rated items are recommended to the user, by employing an efficient ranking process. The paper focuses on a two-level learning process, which is employed on the client side in order to automatically update both user profile models. It involves the use of machine learning algorithms applied to the implicit and explicit user feedback. The system's learning performance has been systematically evaluated based on data collected from regular system users.

Abstract. Nowadays, an increasingly growing demand for advanced multimedia search engines is arising, as huge amounts of digital visual content are becoming available. The contribution of this paper is the introduction of a hybrid multimedia retrieval model accompanied by the presentation of a search engine that is capable of retrieving visual content from cultural heritage multimedia libraries as in three modes: (i) based on their semantic annotation with the help of an ontology; (ii) based on the visual features with a view to finding similar content; and (iii) based on the combination of these two strategies in order to produce recommendations. To achieve this, the retrieval model is composed of two different parts, a low-level visual feature analysis and retrieval and a high-level ontology infrastructure. The main novelty is the way in which these two co-operate transparently during the evaluation of a single query in a hybrid fashion, making recommendations to the user and retrieving content that is both visually and semantically similar. A search engine has been developed implementing this model which is capable of searching through digital libraries of cultural heritage collections, and indicative examples are discussed, along with insights into its performance.

Abstract. Nowadays, an increasingly growing demand for advanced multimedia search engines is arising, as huge amounts of digital visual content are becoming available. The contribution of this paper is the introduction of a hybrid multimedia retrieval model accompanied by the presentation of a search engine that is capable of retrieving visual content from cultural heritage multimedia libraries as in three modes: (i) based on their semantic annotation with the help of an ontology; (ii) based on the visual features with a view to finding similar content; and (iii) based on the combination of these two strategies in order to produce recommendations. To achieve this, the retrieval model is composed of two different parts, a low-level visual feature analysis and retrieval and a high-level ontology infrastructure. The main novelty is the way in which these two co-operate transparently during the evaluation of a single query in a hybrid fashion, making recommendations to the user and retrieving content that is both visually and semantically similar. A search engine has been developed implementing this model which is capable of searching through digital libraries of cultural heritage collections, and indicative examples are discussed, along with insights into its performance.