

![0_image_0.png](0_image_0.png)

five numbers representing the evaluation plus a strength value that indicates the confidence the agent has on this evaluation. Predicates are conceptually organized in different levels and connected by a network of dependencies, specifying which predicates contribute to the values of others. Each predicate in the Repage memory has a set of antecedents and a set of consequents. If an antecedent is created, removed, or changes its value, the predicate is notified, recalculates its value and notifies the change to its consequents. What is of interest in the economy of the present discussion is that in order to make use of Repage's complex network of dependencies we need to aggregate social evaluations, by taking into account what exactly is expressed by the social evaluations.

## 3 The Virtual Market

The experiments reported in this paper ([14], [15],[18] [16], [13] and [17]) were performed in a simulated marketplace in which agents can purchase goods by selecting a seller. This selection is facilitated by the possibility to acquire information from other agents about the quality of sellers or about the quality of other agents as informers. Answers are provided as shared (image) or reported upon (reputation) evaluations.

The market has been designed with the purpose of reproducing the simplest possible setting where information is both valuable and scarce. It includes only two kinds of agents, the buyers and the sellers. All agents perform actions in discrete time units (turns from now on). In a turn, a buyer performs one communication request and one purchase operation. In addition, the buyer answers all the information requests that it receives. Goods are characterized by a utility factor that we interpret as quality (but, given the level of abstraction used, could as well represent other utility factors as quantity, discount, timeliness)
with values between 1 and 100. Sellers are characterized by a constant quality,