Home Page of Zoran Despotovic

Enabling any kind of commerce has as the very first precondition providing appropriate assurance mechanisms that reduce or eliminate opportunistic behavior of the involved parties. Traditional forms of such mechanisms, such as contractual agreements monitored by enforcement institutions, are not always viable in online world. The main reason is that they become totally inefficient when it comes to crossing jurisdictional borders and when the stakes of the involved transactions are small. Under such circumstances, reputation systems as informal social mechanisms for encouraging trustworthy behavior appear to be the only remaining alternative. Their key presumption is that the participants of an online community are engaged in repeated interactions and that collecting, processing, and disseminating information about their past doings is informative of their future behavior and as such will influence it.

The need for reputation mechanisms is particularly strong in P2P systems as potential marketplaces because the participants' personal feelings of autonomy are amplified by the inherent technological decentralization of the environment. However, the decentralization makes the problem of designing reputation mechanisms substantially harder in P2P networks than in centralized settings. There are at least two reasons for this statement: 1) the reputation data retrieval aspect of problem plays an important role in P2P networks and only a small fraction of the entire available feedback can be used and 2) there is no central trusted authority to aggregate feedback in a particular way to enable the decision making process easy or intuitive.

Our findings on the above issues from a short-term project jointly done with professor Jean-Claude Usunier from University of Lausanne can be found here. The follow-up project, joint with the Artificial Intelligence Laboratory of EPFL and Institute of International Management of University of Lausanne, is currently underway.

Once the issue of trust is properly addressed one can think of designing marketplaces on top of P2P platforms. This task implies devising appropriate trading mechanisms but also providing infrastructure for handling payments and exchanges of the traded goods.

In a recent paper I analyzed the existing double auctioning mechanisms in the context of their implementation in P2P networks and proposed a new mechanism that does not rely on the existence of central authorities, auctioneer in particular. As such it is amenable to implementation in P2P environments. The mechanism is a variation of the continuous double auction slightly adapted to fit the decentralized networked environments. It has good economic properties such as, for example, fast convergence towards efficient trading through intuitive and simple bidding strategies.

If the digital goods are traded then it becomes possible to split both the goods to be delivered and the payments into a number of chunks and organize the deliveries of the chunks in such a way that the risks of the involved partners are minimized. If a reputation mechanism tuned to give probabilities of likely behavior of the parties is underlying the exchange then it is also possible to include this aspect of trust into the delivery schedule. This was the problem I also addressed.

My further research interests include more technological aspects of e-commerce such as business process specifications and langages based on XML and accompanying technologies. More specifically, I worked on the problem of creating process-aware user interface based on XSLT processing. The main contribution of this effort was an architecture with a full realization of the separation of concern principle in which the process specification and the target UI were defined separately but seemingly integrated in runtime .

Z. Despotovic and K. Aberer: Probabilistic Prediction of Peers' Performances in P2P Networks, International Journal of Engineering Applications of Artificial Intelligence, Elsevier, forthcoming.
Z. Despotovic and K. Aberer. P2P Reputation Management: Probabilistic Estimation vs. Social Networks, Journal of Computer Networks, Special issue on Management in Peer-to-Peer Systems: Trust, Reputation and Security, Elsevier, forthcoming.
Z. Despotovic, K. Aberer: Maximum Likelihood Estimation of Peers' Performance in P2P Networks, The Second Workshop on the Economics of Peer-to-Peer Systems, Harvard University, Cambridge, MA, USA, June 2004.
Z. Despotovic, K. Aberer: A Probabilistic Approach to Predict Peers' Performance in P2P Networks, Eighth International Workshop on Cooperative Information Agents, CIA 2004, September 27 - 29, 2004, Erfurt, Germany. Awarded 'Best Paper' at CIA2004.
K. Aberer, A. Datta, Z. Despotovic: Separating Business Process from User Interaction in Web-based Information Commerce, Electronic Commerce Research, Volume 3:1-2, January/April 2003, Kluwer Academic Publishers.
Karl Aberer, Philippe Cudré-Mauroux, Anwitaman Datta, Zoran Despotovic, Manfred Hauswirth, Magdalena Punceva, Roman Schmidt: P-Grid: A Self-organizing Structured P2P System, ACM SIGMOD Record, 32(3), September 2003.
Karl Aberer, Philippe Cudre-Mauroux, Anwitaman Datta, Zoran Despotovic, Manfred Hauswirth, Magdalena Punceva, Roman Schmidt, Jie Wu: Advanced Peer-to-Peer Networking: The P-Grid System and its Applications, Praxis der Informationsverarbeitung und Kommunikation (PIK), Special Issue on Peer-to-Peer Systems, 26(3), 2003.
K. Aberer and Z. Despotovic: Managing Trust in a Peer-2-Peer Information System, Proceedings of the Ninth International Conference on Information and Knowledge Management (CIKM), 2001.
K. Aberer, A. Datta, Z. Despotovic: Separating Business Process from User Interaction Utilizing Process-Aware XSLT Style-Sheets, WECWIS 2002.
Z. Despotovic, K. Aberer, M. Hauswirth: Trust-Aware Cooperation, International Workshop on Mobile Teamwork, Vienna, 2002. (position paper).
Z. Despotovic, K. Aberer: Trust-Aware Delivery of Composite Goods, International Workshop on Agents and Peer-To-Peer Computing (AP2PC), Bologna, Italy, 2002.
Z. Despotovic, J.-C. Usunier, K. Aberer: Towards Peer-To-Peer Double Auctioning, Proceedings of the 37th International Hawaiian Conference on System Sciences (HICSS), Waikoloa, Hawaii, USA, 2004.

Tutorials

K. Aberer and Z. Despotovic: Possibilities for Managing Trust in P2P Networks, EPFL Technical Report, IC/2004/84, Lausanne, 2004.
K. Aberer and Z. Despotovic: Managing Trust in a Peer-2-Peer Information System, EPFL Technical Report, IC/2001/029, Lausanne, 2001.
K. Aberer, A. Datta, Z. Despotovic: Separating Business Process from User Interaction Utilizing Process-Aware XSLT Style-Sheets, WECWIS 2002.
Z. Despotovic, K. Aberer: Trust-Aware Delivery of Composite Goods, EPFL Technical Report, IC/2002/019, Lausanne, 2002.
Karl Aberer, Philippe Cudré-Mauroux, Anwitaman Datta, Zoran Despotovic, Manfred Hauswirth, Magdalena Punceva, Roman Schmidt, Jie Wu: Advanced Peer-to-Peer Networking: The P-Grid System and its Applications, EPFL Technical Report IC/2002/73, Lausanne, 2002.
Zoran Despotovic: On Reputation in Game Theory - Application to Online Settings, Working paper, 2004.

Organizing committee member: Fourth International Workshop on Agents and Peer-to-Peer Computing (AP2PC 2005).
Program committee member: The International Conference on Web Technologies, Applications, and Services (WTAS 2005), First International Workshop on Collaborative P2P Information Systems (COPS 2005), SECOVAL 2005 (The Value of Security through Collaboration).
Tutorials at IEEE Conference on E-Commerce Technology (CEC04) and International Conference on Autonomous Agents & Multiagent Systems (AAMAS 2005).
Reviewer for the following journals and conferences: IEEE Transactions on Knowledge and Data Engineering, AAMAS Conference, VLDB Conference, SIGMOD Conference, ICDE Conference, IPTPS Workshop and many others.

I graduated from Faculty of Electrical Engineering (Computer Science Direction) of University of Belgrade, Serbia and Montenegro in 1995.
I am currently Ph.D. student and teaching assistant at Distributed Information Systems Lab at EPFL, Computer Sience and Communication Systems department. I previously completed the pre-doctoral program at the same department (1999-2000), working on a project related to emerging public key cryptographic schemes. Before moving to Switzerland I worked for three years for Yugoslav Chamber of Commerce and Industry. The main focus of my work there was Web development under at that time emerging Java and XML technologies. I had several publications, mostly on Java, and gave numeruous courses on this programming language.
I am a citizen of Serbia and Montenegro.

Zoran Despotovic

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