I've written about controlled digital lending (CDL) before. I'm a proponent of it because I understand how it works legally and its benefits. For me this is one more way libraries are engaged in digital lending in a controlled environment.
I received a question about CDL's own-to-loan ratio and push back received because of ebook licenses and databases which allow more more simultaneous users. How can we explain the limitations of CDL?
First, let's look at ebook and database licenses. When a library licenses a database, it negotiates for how many people it wants to be able to use the database at the same time. Depending on the database and the pricing, the number of simultaneous users may be large. For example, if the number of simultaneous users is 50 and it is not a popular database, then no one may ever get "locked out". However, if 50 people did use the database at the same time, the 51st person would receive a message that they couldn't use the database until someone else finished.
I've seen some expensive databases which libraries license with a low number of simultaneous users in order to control the cost. In those instances, a patron may easily find themselves waiting for someone to stop using the database s they can gain entry.
Ebooks are similar in that a library doesn't license an ebook for an unlimited number of users. It may limited how many users can check out the book at the same time, with an option to increase that number for a while if the book is wildly popular.
With controlled digital lending, the own-to-loan ratio says that if I have one hardcopy, I can loan either the hardcopy or the digital copy, but not both at the same time. In addition, if someone else tries to access the digital copy, while it is already on loan, they will be blocked. The "license"is the number of copies of the book which the library legally owns. If the library want to loan more digital copies through CDL, then it needs to own more legal hardcopies of the work.
Does that analogy work for you?