Are collections sets?

The concept of a collection plays key roles in library, museum, and archival practice, and is arguably fundamental to information organization systems in general. Locating collection concepts in a reasonably robust ontology should have a number of practical advantages, including revealing inferencing opportunities and supporting consistency and coherence in system design and modeling. Although research practices involving collections have been studied empirically there has been surprisingly little attention given to the formal analysis of the concept itself, or to related notions like collection membership. With this paper we hope to convene that discussion, beginning with the question: Are collections sets? We consider in detail the substantial arguments against collections being a kind of set, but argue that at least one version of that claim cannot yet be ruled out. As ontology decisions, both practical and theoretical, are often more a matter of weighing competing considerations than making decisive arguments, progress on this question will probably require the comparison of alternative theories. We invite the information science community to join us in exploring the possibilities.