The ubiquitous use of search engines to discover and access Web content shows clearly the success of information retrieval algorithms. However, unlike controlled collections, the vast majority of Web pages lack an authority asserting their quality. This openness of the Web has been the key to its rapid growth and success, but this openness is also a major source of new adversarial challenges for information retrieval methods.

Abstract. Fully decentralized peer-to-peer (P2P) systems do not have a central control mechanism. Thus, different forms of control mechanisms are required to deal with selfish peers. One type of selfish behavior is the consumption of resources without providing sufficient resources. Therefore, incentive schemes encourage peers to share resources while punishing selfish peers. A well-known example of an incentive scheme is Tit-for-Tat (TFT), as used in BitTorrent. With this scheme, a peer can only consume as much resources as it provides. TFT is resilient to collusion due to relying on private histories only. However, TFT can only be applied to peers with direct reciprocity. This paper presents a private and shared history (PSH) based incentive mechanism, which supports transitive relations (indirect reciprocity). Furthermore, it is resilient to collusion and it combines private and shared histories in an efficient manner. The PSH approach uses a shared history for identifying transitive relations. Those relations are verified using private histories. Simulations show that the PSH mechanism has a higher transaction success ratio than TFT. 1

Trust of information has always been a critical issue in large distributed environments. With the rapid and recent development of online communities and social networks, it has been evident that the Web will rely more and more on user-edited information. As a consequence trust in the correctness of data is falling dramatically and no general solution has been proposed in order to consider that specific but fundamental problem. Trustworthiness on the Internet is usually addressed as a problem of privacy and security(1). So, until now, the solutions to the trust issues are focused on privacy and security. For instance, certificates and the TLS protocol address authentication and data transfer security. The OASIS Consortium addresses information control through the XDI contract links, which are part of the Dataweb architecture (2). This paper is introducing a method for endorsing content correctness based on social participation and the Dataweb paradigm. The general idea is that by creating special XDI contract links supporting trusty-trustee relationships (XDI Trust Information(XTI) contract links), people will be able to estimate the correctness of information using collective intelligence or give their trust to any data for improving the social perception of its correctness. In the future, a new generation of web browser would be able to use the power of XTI and the Dataweb architecture in order to give people a critical view of information. For spreading the technology it should be necessary to fully specify XTI and integrate it in XDI and make it an Internet standard. However, this cannot be done at the moment since the first official release of the XDI specifications is expected before April 2009.

ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof.ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op dinsdag 1 maart 2011 om 12:30 uur door Michel MEULPOLDER ingenieur in de technische informatica geboren te Arnemuiden, NederlandDit proefschrift is goedgekeurd door de promotor:

Abstract not found