In this paper we propose an architecture of e-learning systems characterized by the use of Web services and a suitable middleware component. These technical infrastructures allow us to extend the system with new services as well as to integrate and reuse heterogeneous software e-learning components. Moreover, they let us better support the "anytime and anywhere" learning paradigm. As a matter of fact, the proposal provides an implementation of the run-time environment suggested in the sharable content object reference model (SCORM) to trace learning processes, which is also suitable for mobile learning.