Mobile autonomous systems like robot swarms or mobile software agents operate in a dynamic environment pertaining self-organization, self configurationand heterogeneity of computing entities.In such settings there is a need for autonomicpublishing and discovery of resources and just-in-timeintegration for on-the-fly service consumption withoutany a priori knowledge of available services both withinthe execution environment and from the outsideworld. We propose a mediator-based distributed Webservices discovery and invocation middleware.Moreover we present experimental results on animplemented robot swarm simulation environment. Wepropose a conceptual classification of computingentities on the basis of communication capabilities andconceptual overlay formation for query propagation.Our approach provides a loose coupling in terms ofspace and time and uses both Internet-basedcommunication and RDF-based communication viamessages mediators/post-boxes between entities wheninter-communication between entities is not possible.