This document summarizes a presentation on attribute-based access control models. It discusses the evolution of access control models from discretionary access control and mandatory access control in the 1970s to role-based access control in 1995. Attribute-based access control is presented as the next evolution, allowing flexible, automated and adaptive access control policies based on attributes. The presentation outlines some shortcomings of role-based access control that attribute-based access control aims to address through a more flexible approach using attributes. An ABACα model is proposed as an initial step to unify discretionary, mandatory and role-based access control under a common attribute-based framework. Ongoing and future research directions on attribute-based access control are also mentioned