Simple System of Systems Network (SSSN)

Simple System of Systems Network (SSSN) is the protocol and service layer for semantic channels in PSI services.

The center model is Channel: a named semantic data interface. Stores, brokers, databases, feeds, object stores, graph stores, and local filesystems are backing implementations under that stable protocol. The first backend is deliberately boring: SQLite for metadata and a filesystem directory for artifacts.

Local Store

from sssn import Event, LocalStore

store = LocalStore(".sssn")
store.create_channel({"name": "events", "form": "log"})
event = store.append_event(
    Event(channel="events", source="demo", kind="raw", payload={"text": "hello"})
)

assert store.query_events("events")[0].id == event.id

Default layout:

.sssn/
  sssn.sqlite
  artifacts/

Resources

• Channel: named semantic data interface.
• Event: timestamped semantic record in a channel.
• Subscription: consumer cursor over one channel.
• Artifact: larger payload stored by reference.
• Snapshot: latest state or materialized view.

SSSN does not control services. It provides the channel protocol those services can read from and write to.

Errors And Cursors

Store methods raise stable SSSNError subclasses for missing resources and invalid request values. after_cursor starts at 0, cursors must be non-negative integers, and subscription/query limits must be greater than 0. Returned events include cursor when the backing store can provide one; pass that value back as after_cursor to continue a query. Local stores reject event parent_ids that do not point at existing events. Subscription filters currently support only {"kind": "..."} for event-kind specific consumer loops; unsupported filter keys are rejected instead of being ignored. HTTP clients can call get_subscription() to inspect persisted cursor state.

HTTP clients raise SSSNClientError with status_code, error_type, message, and raw detail fields copied from the server error envelope.

Package Metadata Helpers

SSSN does not own psi.toml, but it can export channel and snapshot metadata for PsiHub:

from sssn import Channel, Snapshot, channel_resource, snapshot_resource

resource = channel_resource(Channel(name="events", schema="demo.schemas:Event"))
latest = snapshot_resource(
    Snapshot(name="latest", channel="events", schema="demo.schemas:Event"),
    description="Latest event state.",
)

Custom SSSN endpoint decorators can be included so generated package cards show domain routes alongside the portable channel API. Use @endpoint.get, @endpoint.post, @endpoint.put, @endpoint.patch, or @endpoint.delete with scope="channel" on channel-specific routes and scope="snapshot" on latest-state routes so package cards can group them correctly.

examples/psihub_manifest shows how to turn channel resources into a PsiHub-style manifest section:

from sssn import Channel, Snapshot, channel_resource, snapshot_resource

raw = channel_resource(
    Channel(
        name="raw",
        schema="raw_event",
        form="log",
        description="Incoming events.",
    )
)
latest = snapshot_resource(
    Snapshot(name="latest", channel="raw", schema="raw_event")
)

manifest = {
    "package": {"org": "demo", "name": "events", "kind": "channel"},
    "channels": {raw["name"]: {k: v for k, v in raw.items() if k != "name"}},
    "snapshots": {latest["name"]: {k: v for k, v in latest.items() if k != "name"}},
}

Resolve Package Refs

PsiHub owns generated .psi/config.toml files, but SSSN can read the shared config shape for channel and snapshot refs:

[refs."psi://demo/events/channels/raw"]
store = ".sssn"

[refs."psi://demo/events/snapshots/latest"]
store = ".sssn"

from sssn import SSSNResolver

resolver = SSSNResolver.from_config(".")
store = resolver.local_store("psi://demo/events/channels/raw")

SSSNResolver ignores refs owned by other layers, such as LLLM tactics and services, so one local config file can bind a composed workspace.

LLLM Composition

SSSN channels compose with LLLM tactics through a small processor loop: pull pending raw events, run the event payload through a tactic, then append the tactic output to an analysis channel with the raw event as its parent. examples/lllm_tactic_processor/workflow.py shows this path without external services or provider keys.

Serve The Store

For a step-by-step local store walkthrough, see docs/tutorials/first-channel.md.

from sssn import LocalStore
from sssn.server import create_app

app = create_app(LocalStore(".sssn"))

Portable HTTP endpoints include:

• POST /channels, GET /channels, GET /channels/{name}
• POST /events, GET /events?channel=..., GET /events/{id}
• POST /subscriptions, GET /subscriptions/{id}, POST /subscriptions/{id}/pull
• POST /artifacts, GET /artifacts/{id}, GET /artifacts/{id}/metadata
• PUT /snapshots/{name}, GET /snapshots/{name}

Custom endpoints can be mounted alongside the portable API:

from sssn.server import create_app, endpoint

@endpoint.get("/channels/{name}/count")
def count_events(store, name: str):
    return {"count": len(store.query_events(name))}

app = create_app(LocalStore(".sssn"), custom_endpoints=[count_events])

Call A Server

from sssn import AsyncSSSNClient

client = AsyncSSSNClient("http://127.0.0.1:7700")
channel = await client.create_channel({"name": "events"})
event = await client.append_event({"channel": channel.name, "payload": {"ok": True}})
same_event = await client.get_event(event.id)

SSSNClient provides the same shape for synchronous code. Subscription creation accepts an optional subscription_id; if that id already exists, the existing subscription is returned so processors can keep a stable cursor across restarts. Reusing an id for a different channel returns a stable conflict error. When write_artifact() receives bytes, HTTP clients send base64 so binary payloads round-trip through the portable API. Artifact writes also accept metadata and event_ids so larger payloads can stay linked to the events that introduced them; local stores reject links to missing events. Artifact downloads use the stored media_type; use get_artifact() to inspect artifact metadata without downloading the payload. Snapshot writes accept a plain value plus optional channel, schema, source_event_id, and metadata fields, or a Snapshot model instance; source_event_id must point at an existing local event.

CLI

sssn --store .sssn create-channel events --schema demo.Event --metadata '{"owner":"demo"}'
sssn --store .sssn get-channel events
sssn --store .sssn append events '{"text":"hello"}'
sssn --store .sssn append events '{"text":"child"}' --schema demo.Event --metadata '{"role":"child"}' --correlation-id corr-1 --parent-id <event-id>
sssn --store .sssn query-events events --limit 10
sssn --store .sssn get-event <event-id>
sssn --store .sssn create-subscription events --id worker --kind event
sssn --store .sssn pull-subscription worker --limit 10
sssn --store .sssn get-subscription worker
sssn --store .sssn write-artifact 'hello' --media-type text/plain
sssn --store .sssn get-artifact <artifact-id>
sssn --store .sssn read-artifact <artifact-id>
sssn --store .sssn put-snapshot latest '{"status":"ok"}'
sssn --store .sssn get-snapshot latest
sssn --store .sssn channels
sssn --store .sssn serve --host 127.0.0.1 --port 7700

Service-Style Processing

examples/channel_processor shows the intended service shape: a process pulls events from one channel subscription and appends derived events to another channel. The example is covered by the test suite so it stays executable.

Artifact And Snapshot Example

examples/artifact_snapshot shows the local-store shape for larger payloads and latest-state materialization: append an event, write an event-linked artifact, then update a latest snapshot.