Philipp Kärger

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With increasing usage of Social Networks, giving users the possibility to establish access restrictions on their data and resources becomes more and more important. However, privacy preferences in nowaday’s Social Network applications are rather limited and do not allow to define policies with fine-grained concept definitions. Moreover, due to the walled(More)
Logic Programming paradigms that allow for expressing preferences have drawn a lot of research interest over the last years. Among them, the principle of ordered disjunction was developed to express totally ordered preferences for alternatives in rule heads. In this paper we introduce an extension of this approach called Disjunctive Logic Programs with(More)
Business processes in open distributed environments such as the Web force users to interact with other parties be it users or companies even if they have never had any common transaction in the past. Policy-driven trust negotiations emerged in order to address these situations. But although many policy languages and protocols have been defined, the problem(More)
Access to learning information is still restricted due to the lack of technical and semantic interoperability, locking knowledge resources in disconnected islands. This situation does not provide learners with a motivating environment in which to access and share learning information. In order to target emerging needs for lifelong competence development, a(More)
Nowadays, people are in need for continuous learning in order to keep up to date or to be upgraded in their job. An infrastructure for life-long learning requires continuous adaptation to learners’ needs and must also provide flexible ways for students to use and personalize them. Controlling who can access a document, specifying when a student may be(More)
While the growing number of learning resources increases the choice for learners, it also makes it more and more difficult to find suitable courses. Thus, improved search capabilities on learning resource repositories are required. We propose an approach for learning resource search based on preference queries. A preference query does not only allow for(More)
The Semantic Web is constantly gaining momentum, as more and more Web sites and content providers adopt its principles. At the core of these principles lies the Linked Data movement, which demands that data on the Web shall be annotated and linked among different sources, instead of being isolated in data silos. In order to materialize this vision of a web(More)
Based on our recent observations at the 7th International Semantic Web Conference and some related workshops as the "Social Data on The Web" one [1], as well as other frequent discussion threads on the Web, trust and privacy on the Social Web remains a hot, yet unresolved topic. Indeed, while Web 2.0 helped people to easily produce data, it lead to various(More)
We propose a mediator architecture that allows a learning system to retrieve learning objects from heterogeneous repositories. A mediating component accepts queries formulated in a uniform query language, translates them into repository specific queries and passes them to each connected repository. For the translation of queries, a novel ontology-based(More)