In ActivityPub, these are all equivalent:

[reiver@mastodon.social]

In ActivityPub, these are all equivalent:

"type":"Banana"

"type":["Banana"]

"type":{"@ID":"Banana"}

"type":[{"@ID":"Banana"}]

"type":{"id":"Banana"}

"type":[{"id":"Banana"}]

"@type":"Banana"

"@type":["Banana"]

"@type":{"@ID":"Banana"}

"@type":[{"@ID":"Banana"}]

"@type":{"id":"Banana"}

"@type":[{"id":"Banana"}]

#ActivityPub #ActivityStreams #FediDev #JSONLD

[oliviavespera@spacey.space]

@reiver That's... kinda shite.

[steve@social.technoetic.com]

@reiver That's assuming "Banana" is a term defined in the JSON-LD context. Even then, the expanded "Banana" term (e.g., "https://server.example/fruits#Banana" is also valid and equivalent.

[reiver@mastodon.social]

@steve

Yes, you are correct, all those are equivalent, too.

Plus any CURIE form (ex: abc:Banana).

I couldn't fit all those in the 500 character limit.

[trwnh@mastodon.social]

@steve @reiver See https://github.com/w3c/json-ld-syntax/issues/446 for a related issue. JSON-LD @\type IRIs get expanded against a @\vocab prefix, or if one is not present then they get expanded against the @\base, and if *that* can't be determined then they are actually not expanded.

However, you don't have to worry about cases like "＠type":{"＠id":"Banana"} because those are not valid. Per https://www.w3.org/TR/json-ld11/#specifying-the-type you only have to worry about strings and arrays of strings.

Also AS2 compacts @\type to type.

[trwnh@mastodon.social]

@steve @reiver So really, those 12 cases reduce to only the first 2.

[trwnh@mastodon.social]

@OliviaVespera @reiver It's also not correct; only the first 2 cases are valid/compliant. (If ActivityPub didn't define "type" to mean @\type, then it would be only the 7th and 8th cases in that list.)

[steve@social.technoetic.com]

@trwnh @reiver The classic example of this issue is a property like `attributedTo` or its subproperty `actor` (just two of many examples). The range is Object|Link. That means the property value could be URI, an Object, a Link or an array (set) of any combination of URIs, Objects or Links where the URI could be compacted, expanded or a CURIE.

[trwnh@mastodon.social]

@steve @reiver Yup. Makes me wish we used an actual normal/canonical form that was more constrained. Even in the AS2 context I've oft thought @\type: @\id could be a mistake since {id: foo} is usually preferable; also, any non-functional property really ought to be @\container: @\set. those would be backwards-incompatible changes, though. and even if someone defined a simpler easier-to-understand profile, what's the point if people don't use it?

[reiver@mastodon.social]

@trwnh @OliviaVespera

Why do you feel that the 7th & 8th cases are not "valid"?

"＠type":"Banana"

"＠type":["Banana"]

...

At the following, "type" is set as an alias for "@type":

https://www.w3.org/ns/activitystreams.jsonld

But, AFAICT, in JSON-LD creating an alias (such as "type") does not make the original form (such as "@type") invalid.

Are you claiming the 7th & 8th form are invalid JSON-LD?

Or, are you claiming the 7th & 8th form are valid JSON-LD, but invalid ActivityPub?

Or, something else?

[trwnh@mastodon.social]

@reiver @OliviaVespera valid JSON-LD but noncompliant AS2, due to ignoring the term definition for "type".

[evan@activitypub.space]

@reiver@mastodon.social That's not true. Most of those are not correct AS2. Only '"type": "Banana"' is correct.

Activity Streams says, The serialized JSON form of an Activity Streams 2.0 document MUST be consistent with what would be produced by the standard JSON-LD 1.0 Processing Algorithms and API [JSON-LD-API] Compaction Algorithm using, at least, the normative JSON-LD @context definition provided here.

So, assuming that you've defined some Banana extension, your full code might look like this:

{
  "@context": [
    "https://www.w3.org/ns/activitystreams",
    {
      "ext": "https://banana.example/",
      "Banana": {
        "@type": "@id",
        "@id": "ext:Banana"
      }
    }
  ],
  "type": "Banana"
}

If you use a JSON-LD library for parsing your input, all the funky variants you're sharing get canonicalized into one easy-to-use one. And if you use it for formatting your output, you'll always produce nice, clean AS2.

[evan@activitypub.space]

Oh, and if you're using an AS2 type, you don't have to worry about the extra context URL, obvs:

{
  "@context": "https://www.w3.org/ns/activitystreams",
  "type": "Person"
}