# Business logic as federated composition-flows

**Vision:** business logic is part of an object's composition — declared on its **type**,
alongside content grammar + allowed relations. State changes federate over fed-sx; federated
services execute the business logic as durable **flows**.

**Design (decided 2026-07-02):**
- **Activity log = every CID delta** — the federated event source of truth. Any content change
  (new CID, per host/blog--cid-of: content in the record → CID; relations are external → not).
- **Triggers = declared subscriptions** — a type declares named triggers (on-publish, on-relate,
  …); flows fire only on matching ones. (fed-sx `DefineTrigger`: activity-type → flow-name + guard
  + actor-scope.) Log complete, execution precise.
- **Flows = hybrid** — simple logic authored as **SX composition** (the execute-fold: effect/alt/
  each — already live in /workflow-demo); an escape hatch to named **Erlang flows**
  (next/flow/*.erl, effect-as-data, deterministic replay, suspend/resume) for the complex.
- **Federated execution = Erlang** (`next/` fed-sx Milestone-1 kernel: trigger_registry +
  flow_dispatch + pipeline post-append fan-out). Authoring stays SX; the fed-sx activity is the
  bridge. flow-on-sx (Scheme, lib/flow) remains for purely-local durable logic.
- **The type carries its whole contract:** fields+grammar (content) · allowed relations
  (external) · triggers+flows (behavior). All composition, all editable in the type-def editor.

**Verified baseline:** `next/tests/triggers_e2e.sh` = 10/10 — publish activity → trigger →
blog_publish_digest flow (urgent/newsletter-suspend/draft-skip/guard-reject/dedup). This is the
reference P0 wires the live host onto.

## P0 — publish workflow, end-to-end (spike)
Prove: live host publishes a post → fed-sx activity → on-publish trigger → blog_publish_digest.

- [x] **P0.1 — the publish-activity contract (SX side).** host/blog--publish-activity(slug):
  a post record → the fed-sx activity {:type "create" :actor "site" :id <CID> :object {:type
  "article" :category … :slug …}}. category from field-value "category", else first tag, else
  "urgent". + host/blog--post-category. blog 200/200 (3 tests). DONE 2026-07-02.
- [ ] **P0.2 — the dispatch bridge.** On publish (host/blog-edit-submit status→published, or a
  dedicated publish action), emit the activity into the trigger machinery. RUNTIME CHOICE for P0:
  in-process — serve.sh loads next/ kernel + registers the on-publish trigger; host emits via the
  erlang-on-sx bridge (erlang-eval-ast pipeline:apply_triggers). (P3 replaces this with real fed-sx
  delivery over next/kernel/http_server.erl.)
- [ ] **P0.3 — the effect is visible.** The flow's digest_sent effect surfaces (a durable record /
  a DigestSent activity back in the log / shown on the post or a /flows page). Close the local loop.

## P1 — types declare behavior (generalize)
- [ ] A Composition field / the type carries a :triggers list (on-publish → flow-name + guard) —
  edited in the type-def editor, like grammar + relations.
- [ ] A fold turns a type's declared behavior into DefineTrigger + flow registrations at boot.
- [ ] Simple flows authored as SX composition (execute-fold) → compiled/dispatched to the engine;
  complex ones reference named Erlang flows.

## P2 — state-change → activity emission (the CID-delta event source)
- [ ] Every content mutation (new CID) appends a state-change activity to the log. Define the
  activity envelope (verb, actor, object CID, prev CID, delta summary).
- [ ] Wire the host's write path (put!/set-comp!/edit-submit) to the append.

## P3 — federation proper
- [ ] Activities cross peers via next/ delivery (http_server / outbox / follower_graph). A remote
  service's trigger_registry fires the flow. Everything works over fed-sx.

## P4 — close the loop
- [ ] Flow effects mutate objects back durably (a flow's DescribeEffects → host writes / new
  activities), so business logic can change state, which federates, which triggers more flows.

## Progress log (newest first)
- 2026-07-02 — P0.1 done. host/blog--publish-activity + host/blog--post-category; the publish
  contract in SX, 200/200. Verified next/ triggers e2e baseline 10/10. Roadmap anchored. NEXT:
  P0.2 the dispatch bridge (in-process: serve.sh loads next/ kernel + registers the on-publish
  trigger; host emits the activity via the erlang-on-sx bridge to pipeline:apply_triggers).