Ambient Assisted Living (AAL) is lacking a reference model that can serve as a basis for understanding the main issues to be addressed without any solution bias. Such a reference model will facilitate consensus-building processes and consolidation efforts towards converging conclusions on AAL infrastructures. The universAAL project, that aims at producing an open platform along with a standardized approach for making it technically feasible and economically viable to develop AAL solutions, has defined a process consisting of four iterations for filling this gap. Here, the results of the first iteration on a reference model for AAL are presented.