This was just the question I wanted to ask, We could have one general set of URI schemes like http://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml, and use different subsets for specific checkers when we want a new one, at first I'll just do like you suggested a very general one and then an HTTP specific one. A lot of the these URIs have crazy semantics though so this could be a rabbit hole, don't know how detailed we want to go here.