Self-adaptive systems modify their own behaviour in response to stimuli from their operating environments. The major policy considerations for such systems are determining what, when and how adaptations should be carried out. This paper presents mechanisms for feedback and change that support policy decisions for self-adaptation within a computationally complete architecture description language based on the π-calculus. Our contribution is support for feedback through software-encoded probes, gauges and an event distribution network together with support for change through decomposition, reification, reflection, recomposition and hyper-code.