Publications by Zoran Despotovic

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This thesis is concerned with enabling e-commerce applications in decentralized environments, P2P networks in particular. The work goes along the following two dimensions: P2P reputation systems design and building P2P e-commerce services and applications. ...

Microblogging sites are a unique and dynamic Web 2.0 communication medium. Understanding the information flow in these systems can not only provide better insights into the underlying sociology, but is also crucial for applications such as content ranking, ...

Wireless ad hoc networks are inherently vulnerable, as any node can disrupt the communication of potentially any other node in the network. Many solutions to this problem have been proposed. In this paper, we take a fresh and comprehensive approach, simultaneously addressing three aspects: security, scalability and adaptability to changing network conditions. Our communication protocol, Castor, occupies a unique point in the design space: it does not use any control messages except simple packet acknowledgm

In the web context, it is difficult to disentangle presentation from process logic, and sometimes even data is not separate from the presentation. Consequently, it becomes crucial to define an abstract model for business processes, and their mapping into an active user interface presentation, using the principle of separation of concern between the process logic, data and its presentation aspects. We endeavor to extend declarative (rule based) XSLT to accommodate the separation of process information from t

In peer-to-peer content delivery systems, such as BitTorrent, there may exist nodes that are non-cooperative and do not contribute their upload bandwidth to the system while still downloading content from others. The current widely used countermeasures aga ...

Reputation systems offer a viable solution to the old problem of encouraging trustworthy behavior in online communities. Their key presumptions are that the participants of an online community engage in repeated interactions and that the information about their past doings is informative of their future performance and as such will influence it. Thus, collecting, processing, and disseminating the feedback about the participants' past behavior is expected to boost their trustworthiness. We investigate and cl

In mobile teamwork environments two basic problems exist: how to discover someone based on a profile (skills, reputations) and how to assess that person’s “credibility” (trust). A lot of work has been done on the issues of collecting and spreading reputations and subsequent computation of trust. The application of such data for decision making, however, is still missing. In this paper we present a solution for scheduling exchanges among participants of an online community which take into a

The limitations of client/server systems become evident in an Internet-scale distributed environment. Peer-topeer (P2P) systems offer an interesting alternative to traditional client/server systems: Every node acts both as a client and a server and “ ...

The database and information retrieval communities have long been recognized as being irreconcilable. Today, however, we witness a surprising convergence of the techniques used by both communities in decentralized, large-scale environments. The newly emerging field of reputation based trust management, borrowing techniques from both communities, best demonstrates this claim. We argue that incomplete knowledge and increasing autonomy of the participating entities are the driving forces behind this convergenc

In sufficiently large heterogeneous overlays message loss and delays are likely to occur. This has a significant impact on overlay routing, especially on longer paths. The existing solutions to this problem rely on message redundancy to mask the loss and d ...

The vast majority of the interactions in typical online communities nowadays is between complete strangers. In such settings reputation reporting and trust management models play a crucial role for proper functioning of those communities. A lot of work has been done on the issues of collecting and spreading reputations and subsequent computation of trust. The application of such data for decision making, however, is far less explored. In this paper we present a solution for scheduling exchanges among partic

Trust and reputation systems have proven to be essential to enforcing cooperative behavior in peer-to-peer networks. We briefly describe the current approaches to building reputation systems: social networks formation, probabilistic estimation and game the ...

The correct functioning of a peer-to-peer network relies on cooperative behavior of peers as service providers. Current approaches to detection and deterrence of non-cooperative behavior, such as reputation systems, rely on (1) global sharing of observatio ...

Managing trust is a problem of particular importance in peer-to-peer environments as one encounters frequently unknown agents. Existing methods for trust management based on reputation do however not scale as they rely on some form of central database or global knowledge to be maintained at each agent. In this paper we illustrate that the problem needs to be addressed at both the data management and the semantic, i.e. trust management, level and we devise a method of how trust assessments can be performed b

In Web-based information commerce it is diffcult to disentangle presentation from process logic, and sometimes even data is not separate from the presentation. Consequently, it becomes crucial to define an abstract model for business processes and their ma ...

Simulators are an excellent tool for quick systems prototyping and large-scale parameter sweeps, but they cannot match the accuracy of live network evaluations. Switching from the simulation to the actual implementation often requires a considerable development effort. Network I/O implementation, measurement instrumentation, deployment automation and distributed debugging are among the most time consuming tasks that the developers face. Moreover, large parts of the application code existing in the simulator

We present ProtoPeer, a peer-to-peer systems prototyping toolkit that allows for switching between the event driven simulation and live network deployment without changing any of the application code. ProtoPeer exports a set of APIs for message passing, me ...

Self-organizing structured peer-to-peer systems.

Zoran Despotovic

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Building trust-aware P2P systems : from trust and reputation management to decentralized e-commerce applications

Outtweeting the Twitterers - Predicting Information Cascades in Microblogs

More on Castor: the Scalable Secure Routing for Ad-hoc Networks

Separating Business Process from User Interaction Utilizing Process-Aware XSLT Style-Sheets

Leveraging Social Networks for Increased BitTorrent Robustness

Possibilities for Managing Trust in P2P Networks

Trust-Aware Cooperation

Castor: Scalable Secure Routing for Ad Hoc Networks

Advanced Peer-to-Peer Networking: The P-Grid System and its Applications

On the Convergence of Structured Search, Information Retrieval and Trust Management in Distributed Systems

Self-organized fault-tolerant routing in peer-to-peer overlays

Trust-Aware Delivery of Composite Goods

The Complex Facets of Reputation and Trust

Authentication-free fault-tolerant peer-to-peer service provisioning

Managing Trust in a Peer-2-Peer Information System

Separating Business Process from User Interaction in Web-Based Information Commerce

ProtoPeer: Distributed Systems Prototyping Toolkit

ProtoPeer: from Simulation to Live Deployment in One Step

P-Grid: a self-organizing structured P2P system

ProtoPeer: A P2P Toolkit Bridging the Gap Between Simulation and Live Deployment