Should the "Prior Art" and "Public Domain" tags be made synonyms of each other? Or is it separate enough and distinct that they should remain separate tags?
I would leave them separated.
- Not all prior art must be in the public domain. Consider an active patent, which could count as prior art.
- Not all questions about public domain materials (even within the scope of this site) are related to prior art. Consider questions about how patent documents enter the public domain, or what that may mean to the patent holders.