The traditional approach to developing middleware platforms is to adopt a "
black box" philosophy whereby the platform offers a fixed programming model
to applications together with fixed per-platform implementations. In this
paper, we describe research which is exploring an open approach to the impl
ementation of middleware platforms, Our motivation is to accommodate the de
manding requirements for quality-of-service (QoS) adaptation as imposed by
mobile multimedia applications. We use an extended CORBA computational mode
l featuring the concept of explicit open bindings, This provides an archite
ctural framework for openness and QoS adaptation. The paper concludes by co
nsidering the more general application of an open systems philosophy; in pa
rticular, we introduce the concept of reflective middleware.