No one layer corresponds to one type of institution. Instead, different institutions can own and operate one or more of the different layers, depending on their mandate, expertise, and negotiated agreements with other parties.
	Rather than a 'one size fits all' or a 'best compromise' approach, this system carves out a significant amount of decision-making for rights holders, librarians, and third parties serving patrons. In addition, over the time scales involved, there will be significant legal, cultural, social, economic and technical changes – new laws, new institutions, new technologies. We have tried to design an architecture whose principles will remain viable irrespective of such changes.
	In addition, we believe that this system passes the critical test of scalability. Because the system only requires simple, well-defined connections between a small number of basic elements, and because those elements are not required to be strongly coordinated with one another, we believe that it can grow to significant scale without breaking down under the weight of coordination costs.