one to indicate that a digital instance can be digitally lent in the framework of Controlled Digital Lending where only one (digital or physical) copy can be lent at a time, and thus the physical copy cannot be lent if we lend the digital copy. Most of our image instances are like this except those from LTWA where the physical copy is circulating there
one to indicate the overall quality of digital instances, so that we can give warnings to our users, acknowledging the low quality (and apologizing)
We need two properties: