This presentation summarizes research on conceptualizing library collections in the digital world. Initial findings from interviews with librarians and social enterprise stakeholders revealed three definitions of "collection": as a process of selection and curation; as a store or grouping of materials; and as access to information resources. A proposed revised collection development hierarchy redefines collections at the strategic, tactical and operational levels. Examples are given for how this could apply to practices like patron-driven acquisitions and institutional repositories.