What can DOIs be assigned to?
DOIs can be assigned to digital files which are the actual “product”, but it is worth emphasising that a DOI need not resolve directly to the object it identifies. For example, an e-book may be a chargeable item, so its DOI may lead the user to a “shopping basket” page with the item already added to the basket; another item may only be available to subscribers, leading the user to a log-in page before the actual item is revealed.
