This is a repository for experiments with defining JSON Schema for Fediverse protocols.
Schemas have currently been created for :
- Activity Streams 2.0
- ActivityPub
- Mastodon ActivityPub
- JSON Resource Description (JRD, Webfinger, NodeInfo)
This git repository contains several submodules so you need to clone it using the --recurse-submodules option.
git clone --recurse-submodules <repo-url>
If you forget to use the extra option, you can initialize the modules with:
git submodule update --init --recursive
To run the tests, you'll need to use poetry to install the package.
poetry install
and then run the pytest tests:
poetry run pytestor
poetry shell
pytestThe schemas are stored in the schemas directory. I use subdirectories to manage the complex schemas.
The test documents are are in the tests\docs directory.
Rather than one large file, the schemas are currently separated into files that generally correspond to a "type" in the related protocol. In the future, I may consider writing a script to combine the files into one schema file.
The schema ids are in the form schema:<path> and, in Python, I use a resolver to map the schema id to the directory and file containing the schema.
Note that JSON-LD data is preprocessed to remove any object keys with null values. These are noise since they ignored in a JSON-LD data model and handling them in the schema makes it much more complex.
The JSON-LD documents are also tested to be sure they can be expanded using the standard JSON-LD expansion algorithms. There is no check that the results make sense from an ActivityPub perspective.
Experimental JSON Schema for defining AS2 message constraints and metadata.
The top-level schema is in as2/activitystreams2-schema.json. This references type-specific schemas. There are also two special schemas for untyped messages and messages with only extension properties.
Note that all properties are optional in AS2. The {} document is valid. Specifically, this leads to a somewhat surprising fact that type is optional so untyped documents are also valid. The JSON-LD @context is optional but a consumer must assume the standard AS2 context (i.e., inject it if it's missing) when using JSON-LD expansion.
Properties can be inherited from a parent type like Object, Links or Activity (and others). To support this inheritance and still validate type-specific properties, any type that has subtypes has their schema split into a <type>-schema.json file and a <type>-base-schema.json file. Subtypes will then reference the <type>-base-schema.json to inherit that base type's constraints. This can happen recursively if there are multiple levels of inheritance.
This is a specialization of AS2 that adds new, required and optional properties to the actors (e.g., inbox, endpoints, ...).
(This is a WIP.) The Mastodon schema significantly constraints the AP schema. Mastodon supports only a small subset of the AP/AS2 data model.
I'm starting to investigate how many of the Mastodon-specific constrains can be represented in JSON Schema. For example, Mastodon allows a list of types to be specified for an AP Object, but not for an AP Activity.
These schema describe the JRD format used by Webfinger and the top-level link list for the nodeinfo protocol.