: In the recent years, XML has become the universal interchange format. Many investigations have been made on storing, querying and integrating XML with existing applications. Many XMLbased commercial DBMSs have appeared lately. This paper reports on the analysis of an XML mediator federating several existing XML DBMSs. We measure their storage and querying capabilities directly through their Java API and indirectly through the XLive mediation tool. For this purpose we have created a simple benchmark consisting in a set of queries and a variable test database. The main scope is to reveal the weaknesses and the strengths of the implemented indexing and federating techniques. We analyze two commercial native XML DBMS and an opensource relational to XML mapping middleware. We first pass directly the queries to the DBMSs and second we go through the XLive XML mediator. Results suggest that text XML is not the best format to exchange data between a mediator and a wrapper, and also shows som...