rose-ash/plans/composition-objects.md

Composition objects — a content-addressed, data-driven UI model

Everything the system stores is an object: typed, content-addressed (:cid), in one graph. "Post" was the blog's word; the unit is an object. A document is an object whose body is a composition over other objects' CIDs. This is the cards-as-objects decision, generalised.

One mechanism: ordered, labelled forks

An object forks into children via labelled, ordered edges (the relations engine + order on the edge value + an optional when). There is no separate "composition system" — relations are the forks. The label says what a fork means:

• structural (contains) → ordered, part of identity, rendered;
• cross-cutting (tagged, related, author) → loose links, not structural.

Multiple relations from an object are its fork. No "multiple DAGs per object" — fork immediately; differently-labelled forks (body vs aside) give named slots. Join = a child CID referenced by two forks — free, because content-addressed. The whole structure is a Merkle DAG (git trees / IPFS / artdag): :cid = hash over fields + contains-forks (child-CID + order + when).

The body is a tiny UI language (the render-fold is its interpreter)

A body is a composition node. Four combinators + leaves + references:

node	meaning	strategy
(seq …)	sequence	render all (block), in order
(row …) / (grid …)	layout (par)	render all, side-by-side
(alt (when P n) … (else n))	conditional (or)	render the FIRST child whose when holds
(each src tmpl)	iteration (loop)	eval src → items; render tmpl per item (item bound)
(ref CID)	transclude	fetch object by CID, render its body
(card TYPE fields)	leaf	render via the card-type's :template (host/blog--instantiate)
(tmpl NAME)	recursion	a named template, may reference itself

seq/row = render-all passing children; alt = render-first passing child. So and/or/choice all come from one axis (when on forks) × the container's all/first strategy — Alt isn't a new node kind, it's "first" instead of "all".

The two fundamentals we designed IN

1. Recursion — (tmpl NAME) may reference itself; (each (children) (tmpl NAME)) renders trees (comment threads, nested nav, the /meta type hierarchy itself). Terminates naturally when a query runs dry; a depth guard in the context backstops it.
2. The context is an environment, not a flat dict. when reads it; each extends it (:item). Make it extensible + reactive-ready and the two non-composition axes plug in with NO new combinators:
   • Behaviour / interactivity (Slice 9 lifecycles/effects) — a button references a behaviour;
   • Reactivity / local state (the reactive runtime) — alt(when local-state=active-tab) is a tabset, alt(when accordion-open) an accordion; a live each re-renders on data change. The static render-fold becomes a live, interactive UI purely by making the context live.

The unifying property

The object's CID is its definition (the query, the template, every when-variant). The rendering is the execution (which items, which branch, which context). The object is the program; the render is the run. One immutable content-addressed object encodes its whole responsive/personalised/variant space; rendering picks the path. Render-fold and the Slice-9 behaviour interpreter are the same shape — interpreters over content-addressed objects + the decidable-core predicate set + the graph. The system converges on: objects + small interpreters.

What lives elsewhere (not composition primitives)

Transclusion = a ref leaf. Sort/filter/limit/group = the source query language (Datalog). each reconciliation keys = the item's CID (free). Empty / missing-CID = render-fold robustness (the per-block guard). Async/streaming, events, local state = the behaviour + reactive axes.

Build roadmap

1. Keystone (this): lib/host/compose.sx — the render-fold interpreter over seq/row/alt/each/ ref/card/tmpl, with the context-as-environment, when predicates, and recursion + depth guard. Self-contained proof: render one composed object two ways (auth on/off) + a recursive tree.
2. Wire it to objects: a document's :body is a composition node; contains forks carry order; host/blog-render dispatches to the render-fold when :body is present (else the legacy sx_content path). Card leaves render via the existing card-type :template.
3. each source = a graph query ((query is-a Event) → host/blog-instances-of) — data-driven.
4. Live context: route auth/device/locale into the context; reactive values later.
5. The typed importer decomposes Ghost Lexical into card objects + a contains body (cards-as- objects), instead of one sx_content string.
6. The block editor edits the body (insert/reorder/alt/each) — the metamodel editor for content.