We present a new taxonomy for describing the conditions and implementation of interactions. Current mechanisms for embedding interaction in software promote a hard separation between the programmers who produce the software, and the communities who go on to use it. In order to support open ecologies of function and fabrication, where this separation is negotiated by communities of users and designers, we need to reconceive those mechanisms. We describe interaction in two phases: Co-occurrence, the prerequisite conditions for an interaction to take place; and entanglement, the temporary coupling and interplay between elements participating in the interaction. We then sketch a blueprint of a system where those phases and their adjacent mechanisms enable communities of users to build and use interactive software. There are many ways of conceiving this new design space, and we present three dominant metaphors which we have employed so far, based on chemical reactions , quantum physics and cooking. We exhibit different systems which we have implemented based on these metaphors, and sketch how future systems will further empower citizens to design and inhabit their own interactions, express ownership over them and share them with communities of interest.