I am periodically upset that ActivityPub does not mandate a closed json-ld context for all objects.

[trwnh@mastodon.social]

@gugurumbe that seems to be several completely separate issues to me. before any communication becomes possible, we have to agree on terms. after we agree on terms, we can make statements. but statements can be unavailable, false, outdated, etc. -- your understanding of the statements remains unaffected.

you can think of contexts as "obfuscation", but they are really just "definitions". the question is, should you expect everyone to provide definitions? and there are two levels of definitions.

[trwnh@mastodon.social]

@gugurumbe the first level is mapping a shorthand term to a full identifier. this is what json-ld does, if you care to do it. you can make json-ld optional by requiring everyone to use full identifiers always.

the second level is mapping identifiers to concepts. this is more based on social agreement, but with http(s): identifiers there is an easy "hack" -- just use the authority component (web origin) to determine who gets to define what identifiers mean. whatever they say is whatever goes.

[trwnh@mastodon.social]

@gugurumbe fedi devs skip over these levels and go straight from a shorthand term to a concept. the problem with this is that no one "owns" the shorthand terms, so you can't get an authoritative answer on what anything means. you have to defer to some kind of lookup table, and everyone you talk to has to agree to use the same one. just like everything the IANA does with their central registries, but in fedi we do not have any authorities, so shorthand terms are defined by consensus only.

[gugurumbe@mastouille.fr]

@trwnh the understanding of the statements in the document may be different between the receiver and the sender, if the context dereferences to different term definitions for both parties.
Obfuscation is a different story, but it can be used to partially prevent human review of the data if something goes wrong.

[trwnh@mastodon.social]

@gugurumbe so if you see a term "featured", it has effectively been claimed by Mastodon through prior use and most people assume the Mastodon definition. just like people see "actor" and assume it means "who performed this Activity" and not "who performed a character role in a movie", except in the latter case we have an actual definition by the W3C inherent to the media type of application/activity+json, and in the former case we do not have any way to disambiguate.

[trwnh@mastodon.social]

test refederation

[trwnh@mastodon.social]

test refederation

[trwnh@mastodon.social]

test refederation

[thisismissem@activitypub.space]

gugurumbe@mastouille.fr iirc, general best practice in JSON-LD is to either preload contexts or to fetch and cache indefinitely, unless you encounter a new property you don't understand, and then refetch and cache.

[gugurumbe@mastouille.fr]

@thisismissem Caching is why the server hosting the context can declare wrong term definitions even if it only lied in the past.