Business collaborations in Virtual Organisations (VOs) demand sound security infrastructures to achieve acceptance from industry. It becomes apparent that in dynamic environments requiring swift decisions as well as quickly adapted and connected applications, traditional hard security e.g. based on static access control is no longer able to cope with security alone to meet the collaboration objective. Soft security based on trust management, e.g. provided by a reputation system, is able to address those requirements dealing with previously unknown entities and hereby complement, but not replace, established static hard security. This paper introduces a novel approach and proposed architecture for a trust management system providing reputation, rooting trust in a collaborating entity?s inherently characterizing trust parameters. Those parameters are stochastically modelled aiming at capturing the real parameter?s behaviour and aggregated with stochastic system theory. This approach is believed to retain the quality of a model with implicit semantic behaviour of trust parameters from the root of trust, the observed parameters, to the aggregated reputation provided as decision support to applications.