@julian @helge the fundamental root of the issue is that to/cc/audience are `type:id`, whereas `Public` is a vocab term. because of the way prefixing works in jsonld, the ONLY "correct" representation is as:Public. the full iri ALWAYS gets compacted to the prefixed one, and the vocab term definition for `Public` actually has no effect whatsoever outside of properties that are defined as `type:vocab`... of which, none of the AS2 addressing properties are defined this way. nor should they be!

@julian @helge relevant issue:

Revisit the `https://www.w3.org/ns/activitystreams#Public` == `as:Public` == `Public` equivalence and guidance · Issue #404 · w3c/activitypub

Motivation Continuing from #264 and with this JSON-LD playground link, we make the following observations: First, that the AS2-Core spec requires that AS2 documents are consistent with the JSON-LD compacted form; Second, that within the ...

GitHub (github.com)

specifically https://github.com/w3c/activitypub/issues/404#issuecomment-2406024468

the whole concept of "delivering to the Public pseudo-collection" is conceptually unfounded. what "addressing as:Public" *actually* does is set a visibility class.

@julian @helge

in any case, if you want to be compatible with the most implementations, practically this means using the full iri. i think most implementations have special-cased this iri, so it should generally work.

if you want to be complaint with as2, then use as:Public. no other form is "correct". but you might encounter more implementations that fail to account for this, because i think mastodon sends the full iri, so that's what most implementations account for.

See Note at the end of 5.6 Public Addressing.

might result in https://www.w3.org/ns/activitystreams#Public being represented as simply Public or as:Public which are valid representations of the Public collection.

@helge @julian That note is incorrect. :-))))

AS2-Core requires consistency "with what would be produced" when compacting against the normative context, which in this case is always as:Public.

Getting the full IRI would require dropping the as: prefix.

Getting `Public` would require using a property defined as `type:vocab`. (In other vocabularies, you have a split between type:id and type:vocab terms. AS2/AP neglected to do this.)