In Online Social Networks (OSNs) users are overwhelmed with huge amount of social data, most of which are irrelevant to their interest. Due to the fact that most current OSNs are centralized, people are forced to share their data with the site, in order to be able to share it with their friends, and thus they lose control over it. Decentralized Online Social Networks have been proposed as an alternative to traditional centralized ones (such as Facebook, Twitter, Google+, etc.) to deal with privacy problems and to allow users to maintain control over their data.
This thesis presents a novel peer-to-peer architecture for decentralized OSN and a mechanism that allows each node to filter out irrelevant social data, while ensuring a level of serendipity (serendipitous are social data which are unexpected since they do not belong in the areas of interest of the user but are desirable since they are important or popular). The approach uses feedback from recipient users to construct a model of different areas of interest along the relationships between sender and receiver, which acts as a filter while propagating social data in this area of interest. The evaluation of the approach, using an Erlang simulation shows that it works according to the design specification: with the increasing number of social data passing through the network, the nodes learn to filter out irrelevant data, while serendipitous important data is able to pass through the network
