Nowadays more and more Internet applications install reputation systems to collect opinions users have about some reputation objects. The opinions are usually formalized in the form of ratings the reputation system can use to build overall reputation profiles of the reputation objects. Reputation objects might be other users, products, web content and anything else that can be rated. Users may investigate the reputation object’s reputation profile to estimate its quality resp. trustworthiness. As there are currently many providers of reputation systems it would be desirable to make reputation information in different systems interoperable or to establish meta reputation systems that collect information from various applications resp. their reputation systems. This process should consider both interoperability of reputation systems themselves and their interoperability with applications, trust and identity management systems as we will discuss in this paper.