In this paper we propose an architecture for a Moving Object Server acting as a mediator between queries submitted by web user and events received by the server. Assuming that such a server must be able to support a large amount of queries, we discuss the necessity of designing appropriate data structures to map queries with events. We describe a simple solution relying on an index built on queries, thus avoiding the difficulty of indexing moving objects. Finally our prototype shows that our approach can be implemented with little effort and standard, though advanced, languages and products.