This paper investigates how dynamic properties of reputation can influence the quality of users ranking. Reputation systems should be based on rules that can guarantee a high level of trust and help identifying unreliable units. To understand the effectiveness of dynamic properties in the evaluation of reputation, the authors propose a model that is based on three factors: forgetting, cumulative, and activity period. The preliminary results are presented for different sets of values of the aforementioned factors in order to analyze how effectively the model can be used for modeling reputation systems.
