Subjective logic operators in trust assessment: an empirical study

Computational trust mechanisms aim to produce trust ratings from both direct and indirect information about agents’ behaviour. Subjective Logic (SL) has been widely adopted as the core of such systems via its fusion and discount operators. In recent research we revisited the semantics of these operators to explore an alternative, geometric interpretation. In this paper we present principled desiderata for discounting and fusion operators in SL. Building upon this we present operators that satisfy these desirable properties, including a family of discount operators. We then show, through a rigorous empirical study, that specific, geometrically interpreted, operators significantly outperform standard SL operators in estimating ground truth. These novel operators offer real advantages for computational models of Research was sponsored by US Army Research laboratory and the UK Ministry of Defence and was accomplished under Agreement Number W911NF-06-3-0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the US Army Research Laboratory, the U.S. Government, the UK Ministry of Defense, or the UK Government. The US and UK Governments are authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon. Corresponding author: F. Cerutti. F. Cerutti · T. J. Norman · N. Oren · A. Toniolo University of Aberdeen School of Natural and Computing Science King’s College AB24 3UE, Aberdeen, UK E-mail: [email protected] E-mail: [email protected] E-mail: [email protected] E-mail: [email protected] L. Kaplan US Army Research Laboratory Adelphi MD, USA E-mail: [email protected] trust and reputation, in which they may be employed without modifying other aspects of an existing system.