Powerline delegations MUST NOT be used as the root delegation to a resource. A priori there is no such thing as a null subject.
Why must a powerline delegation not be the first delegation in a proof chain? I'm not sure how the second sentence explains it. The practical effect of a powerline delegation being disallowed as the first delegation is that Alice can use a single delegation to delegate some command /do/something to Bob for every subject she is currently authorized to /do/something to except herself. To delegate /do/something on herself, she has to issue a separate delegation. The first one is a powerline, and can appear in a proof chain where an earlier proof delegates /do/something on some subject to Alice. But when Alice is the subject, her delegation would come first, and we're not allowed to do that.
Is it simply because the powerline is too risky to apply to one's self-sovereign authority, and we only want that to be delegated with an explicit subject? Or is there another reason I'm missing?
Why must a powerline delegation not be the first delegation in a proof chain? I'm not sure how the second sentence explains it. The practical effect of a powerline delegation being disallowed as the first delegation is that Alice can use a single delegation to delegate some command
/do/somethingto Bob for every subject she is currently authorized to/do/somethingto except herself. To delegate/do/somethingon herself, she has to issue a separate delegation. The first one is a powerline, and can appear in a proof chain where an earlier proof delegates/do/somethingon some subject to Alice. But when Alice is the subject, her delegation would come first, and we're not allowed to do that.Is it simply because the powerline is too risky to apply to one's self-sovereign authority, and we only want that to be delegated with an explicit subject? Or is there another reason I'm missing?