"So a key design goal of XDI is to support the requirements of both persistent and reassignable forms of identification; to provide precise means to map between them; and to make it syntactically unambiguous which form is being used in which context."
Shouldn't the 1st sentence say "... to support the benefits of both..." ?
Or remove "the requirements of".
Comment: unlike most other design goals, it is not clear to me how we achieved the aforementioned goals. In particular, I'm not sure where reassignable identifiers are used in XDI? Is it through dictionaries?