ActivityPub Federation & Engineering Morsels

Ansatz implements the W3C ActivityPub standard (Server-to-Server and Client-to-Server) to enable decentralized collaboration among engineers. Rather than confining simulations and discussions to a single walled garden, independent Ansatz nodes can federate, exchange posts, and follow engineers across the network.

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What is an Engineering Morsel?

In conventional social networks, posts consist of plain text, images, or static video. In Ansatz, posts can carry Morsels—rich, structured payloads representing verifiable engineering artifacts:

1. Simulation Runs: Encapsulated DAE/ODE trajectory datasets with time-series plots, parameter configurations, and solver settings.
2. Interactive 3D CAD/FEA/CFD Views: Compressed STEP geometries or VTK Unstructured Grid (.vtu) stress fields viewable directly in the feed using Three.js and WebXR.
3. Schematic & Architecture Diffs: Visual diffs (PolyglotVersionDiffView) showing added, modified, or removed components across Modelica and SysML diagrams.
4. Executable Scripts: Self-contained ModelScript scripts that other engineers can open in /playground with a single click.

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Federation Protocol Details

Actor Identification & WebFinger

Every engineer on an Ansatz node has a federated handle formatted as @[email protected]. Remote instances resolve actor profiles via RFC 7033 WebFinger:

GET /.well-known/webfinger?resource=acct:[email protected]

The server returns a JSON Resource Descriptor pointing to the actor's ActivityPub actor object at /api/v1/users/alice.

Cryptographic Signatures (HTTP Signatures)

Outbound server-to-server HTTP requests are cryptographically signed using HTTP Signatures (draft-cavage) with an RSA-2048 keypair generated during account creation:

• The public key is published in the actor document (publicKey.publicKeyPem).
• Incoming activities are verified against the sender's public key before being accepted into the instance inbox (/api/v1/inbox).

Activity Types

Ansatz supports standard ActivityStreams 2.0 activities:

• Create(Note): Publishing a new engineering post or morsel.
• Follow(Actor): Following an engineer on a remote node.
• Accept(Follow): Confirming a follow request.
• Announce(Note): Boosting or sharing a post to local followers.
• Like(Note): Favoriting an engineering post.
• Delete(Tombstone): Permanently retracting a post.

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Domain Moderation & Federation Policies

Administrators control outbound and inbound federation via the Federation tab in /admin:

Policy Tier	Behavior
Open Federation	Connects to any valid ActivityPub node with verified HTTP signatures.
Domain Allowlist	Only allows federation with explicitly approved partner instances.
Silenced Domain	Remote posts are hidden from public and explore feeds, visible only to direct followers.
Suspended Domain	All incoming and outgoing federation traffic with the domain is blocked.