7. Materials and Themes

7.1 Slots as dependency injection

The structure side never writes a concrete block name; it only carries a mat_slot (an injection point). A theme binds values to slots and selectors (analogous to CSS / dependency injection). This separates structure (where the walls are) from style (which blocks, what detailing).

def cottage class=house size=9x7:
  floor  id=floor  mat_slot=floor
  walls  id=walls  class=outer mat_slot=wall height=4
  roof   id=roof   kind=gable  mat_slot=roof
  window id=front_windows class=small side=front y=2 repeat=2 mat_slot=glass

theme medieval:
  slot wall  -> @cobblestone
  slot roof  -> @spruce_stairs
  walls[class=outer]  -> trim=@spruce_log     # inject part detailing via a selector
  window[class=small] -> frame=@spruce_wood

def, theme, and site are unified by the same slot-bearing Component mechanism (Components, Editing, and Multi-building).

7.2 Canonical vocabulary (canonical token)

The values a theme/slot binds are canonical tokens, not raw block IDs. The backend resolves the ID, state names, state values, and serialization per (edition, version) (Versioning and Editions). An LLM never needs to know pillar_axis, little-endian NBT, or Bedrock’s weirdo_direction.

Canonical tokens come in two tiers:

• canonical block token (a meaning in Minecraft): @oak_planks @water_cauldron @oak_log[axis=x]. Silent meaning-breaking downgrades are forbidden (e.g. @water_cauldron → cauldron is not allowed).
• abstract material token (an aesthetic choice): @floor.wood.broadleaf @roof.dark_wood. Theme policy MAY downgrade these (e.g. oak↔birch).

theme cottage:
  slot floor -> @floor.wood.broadleaf   # abstract: resolved to a concrete material by target/policy
theme exact_oak:
  slot floor -> @oak_planks             # canonical: pinned 1:1

7.3 Mappings across version and edition

A canonical token absorbs the following five patterns (the resolution table structure is in Versioning and Editions):

Pattern	Example	Policy
rename 1:1	@dirt_path (grass_path→dirt_path)	auto-resolve
split 1:N	@cauldron[fluid=water] (cauldron→water_cauldron)	separate by meaning token
merge N:1	@oak_slab (wooden_slab{variant}→oak_slab)	resolve per target
new	@cherry_planks	requires requires >=
deleted	(absent in the target version)	hard error + alternatives

Only ID/state/serialization differences may be absorbed. “Concept absence” and “game-behavior differences” are not absorbed (Versioning and Editions).