I have deeply mixed feelings about #ActivityPub's adoption of JSON-LD, as someone who's spent way too long dealing with it while building #Fedify.
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@hongminhee from the point of view of someone who is "maintaining" a JSON-LD processing fedi software and has implemented their own JSON-LD processing library (which is, to my knowledge, the fastest in it's programming language), JSON-LD is pure overhead. there is nothing it allows for that can't be done with
1. making fields which take multiple values explicit
2. always using namespaces and letting HTTP compression take care of minimizing the transfer
without JSON-LD, fedi software could use zero-ish-copy deserialization for a majority of their objects (when strings aren't escaped) through tools like serde_json and Cow<str>, or System.Text.Json.JsonDocument. JSON-LD processing effectively mandates a JSON node DOM (in the algorithms standardized, you may be able to get rid of it with Clever Programming)
additionally, due to JSON-LD 1.1 features like @type:@json, you can not even fetch contexts ahead of time of running JSON DOM transformations, meaning all JSON-LD code has to be async (in the languages which has the concept), potentially losing out on significant optimizations that can't be done in coroutines due to various reasons (e.g. C# async methods can't have ref structs, Rust async functions usually require thread safety due to tokio's prevalence, even if they're ran in a single-threaded runtime)
this is after context processing introducing network dependency to the deserialization of data, wasting time and data on non-server cases (e.g. activitypub C2S). sure you can cache individual contexts, but then the context can change underneath you, desynchronizing your cached context and, in the worst case, opening you up to security vulnerabilities
json-ld is not my favorite part of this protocol@kopper @hongminhee As the person probably most responsible for making sure json-ld stayed in the spec (two reasons: because it was the only extensibility answer we had, and because we were trying hard to retain interoperability with the linked data people, which ultimately did not matter), I agree with you. I do ultimately regret not having a simpler solution than json-ld, especially because it greatly hurt our ability to sign messages, which has considerable effect on the ecosystem.
Mea culpa
![😕](https://board.circlewithadot.net/assets/plugins/nodebb-plugin-emoji/emoji/android/1f615.png?v=28325c671da ":\")
I do think it's fixable. I'd be interested in joining a conversation about how to fix it.
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@kopper @hongminhee As the person probably most responsible for making sure json-ld stayed in the spec (two reasons: because it was the only extensibility answer we had, and because we were trying hard to retain interoperability with the linked data people, which ultimately did not matter), I agree with you. I do ultimately regret not having a simpler solution than json-ld, especially because it greatly hurt our ability to sign messages, which has considerable effect on the ecosystem.
Mea culpa
I do think it's fixable. I'd be interested in joining a conversation about how to fix it.
I don't remember it that way.
We started the WG off with AS2 being based on JSON-LD, and I don't think we ever considered removing it.
I don't think it was a decision you made on your own. I'm not sure how you would, since you edited AP and not AS2 Core or Vocabulary.
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I don't remember it that way.
We started the WG off with AS2 being based on JSON-LD, and I don't think we ever considered removing it.
I don't think it was a decision you made on your own. I'm not sure how you would, since you edited AP and not AS2 Core or Vocabulary.
I would be strongly opposed to any effort to remove JSON-LD from AS2. We use it for a lot of extensions. Every AP server uses the Security vocabulary for public keys.
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I would be strongly opposed to any effort to remove JSON-LD from AS2. We use it for a lot of extensions. Every AP server uses the Security vocabulary for public keys.
@cwebber @kopper @hongminhee It would be a huge backwards-incompatible change for almost zero benefit. People would still make mistakes in their ActivityPub implementations (sorry, Minhee, but that's life on an open network). We'd need to adopt another mechanism for defining extensions, and guess what? People are going to make mistakes with that, too.
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@cwebber @kopper @hongminhee It would be a huge backwards-incompatible change for almost zero benefit. People would still make mistakes in their ActivityPub implementations (sorry, Minhee, but that's life on an open network). We'd need to adopt another mechanism for defining extensions, and guess what? People are going to make mistakes with that, too.
@cwebber @kopper @hongminhee The biggest downside to JSON-LD, it seems, is that it lets most developers treat AS2 as if it's plain old JSON. That was by design. People sometimes mess it up, but most JSON-LD parsers are pretty tolerant.
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@cwebber @kopper @hongminhee The biggest downside to JSON-LD, it seems, is that it lets most developers treat AS2 as if it's plain old JSON. That was by design. People sometimes mess it up, but most JSON-LD parsers are pretty tolerant.
@evan @cwebber @kopper @hongminhee Couldn’t we agree to standardize on expanded json-ld? We would not need any json-ld processor, we would not need to fetch or cache any context. There would be no way to shadow properties.
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@evan @cwebber @kopper @hongminhee Couldn’t we agree to standardize on expanded json-ld? We would not need any json-ld processor, we would not need to fetch or cache any context. There would be no way to shadow properties.
@gugurumbe @cwebber @kopper @hongminhee AS2 requires compacted JSON-LD.
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@gugurumbe @cwebber @kopper @hongminhee AS2 requires compacted JSON-LD.
@evan @gugurumbe @cwebber @kopper @hongminhee only for terms defined in AS2, though?
if the activitystreams context is missing in an application/activity+json document, then you MUST assume/inject it. this means you can't redefine "actor" to mean "actor in a movie".
otherwise, you don't have to augment the context with anything else. "https://w3id.org/security#publicKey" is a valid property name. the proposal is to not augment the normative context where possible. no parsing context if there is no context
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@evan @gugurumbe @cwebber @kopper @hongminhee only for terms defined in AS2, though?
if the activitystreams context is missing in an application/activity+json document, then you MUST assume/inject it. this means you can't redefine "actor" to mean "actor in a movie".
otherwise, you don't have to augment the context with anything else. "https://w3id.org/security#publicKey" is a valid property name. the proposal is to not augment the normative context where possible. no parsing context if there is no context
@trwnh i was replying to a post that wanted all expanded terms.
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@trwnh i was replying to a post that wanted all expanded terms.
@evan @trwnh @cwebber @kopper @hongminhee I think it would be great to have everything expanded besides the required as2 context.
The results of the compaction algorithm would change if new things migrate into schema.org, so technically a document could become invalid or break without being modified, but this would be a lot better otherwise I guess. -
@evan @trwnh @cwebber @kopper @hongminhee I think it would be great to have everything expanded besides the required as2 context.
The results of the compaction algorithm would change if new things migrate into schema.org, so technically a document could become invalid or break without being modified, but this would be a lot better otherwise I guess.@gugurumbe @evan @cwebber @kopper @hongminhee yup, using full IRIs also has the advantage that ld-unaware processors only need to recognize 1 form instead of infinitely many.
the thing is, we have semantics imported from the content type (activity+json) which can also change. which is why i think versioning the context document is also important -- it freezes the semantics at the time of publishing, like pinning your dependencies.
without that, we might well have a simpler profile...
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@gugurumbe @evan @cwebber @kopper @hongminhee yup, using full IRIs also has the advantage that ld-unaware processors only need to recognize 1 form instead of infinitely many.
the thing is, we have semantics imported from the content type (activity+json) which can also change. which is why i think versioning the context document is also important -- it freezes the semantics at the time of publishing, like pinning your dependencies.
without that, we might well have a simpler profile...
@trwnh as a paranoid person, I sometimes wonder what would happen if schema.org received a court order to partially censor its schema in certain regions of the world. Or inject a backdoor key. If it prevents people from sending memes across the geofence, it’s bad.
