Olav Aarts

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—This literature review is aimed at examining state of the art research in the field of online social networks. The goal is to identify the current challenges within this area of research, given the questions raised in society. In this review we pay attention to three aspects of social networks: actor, message, and network characteristics. We further limit(More)
Surveillance for security requires communication between systems and humans, involves behavioural and multimedia research, and demands an objective benchmarking for the performance of system components. Metadata representation schemes are extremely important to facilitate (system) interoperability and to define ground truth annotations for surveillance(More)
In this paper the influence of interventions on Twitter users is studied. We define influence in a) number of participants, b) size of the audience, c) amount of activity, and d) reach. Influence is studied for four different target groups: a) politicians, b) journalists, c) employees and d) the general public. Furthermore, two types of interventions are(More)
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