Implement OVP

Everything needed to build a conformant parser, renderer, validator, or composer, without asking the authors anything. The reference implementation lives in tools/ in the repository; this page is the contract it implements.

Conformance levels

Level	Name	You can claim it when
1	Parser	you read specs and tokens and validate them against the published schemas
2	Renderer	you reproduce the golden renders for at least one chart family from spec + tokens + data
3	Presenter	you compose recipes (language + charts + components) on the slide canvas
4	Advisor	you use the machine metadata to pick the right object for a message
5	Full	you deterministically reproduce every golden across all built objects

The determinism contract

Same spec + same tokens + same data = the same output. For SVG, byte-identical; for container formats with volatile envelopes (PPTX zip timestamps), member-identical.
Specs carry exact px values and color ROLES. Resolve a role chain like benchmark -> muted to the first role the palette defines.
Merge a spec's overrides[DL-xx] block over the spec before rendering in that language.
Float formatting: at most 2 decimals, trailing zeros stripped, never -0.
Nice-tick algorithm (normative, FN-05): raw = max / target_ticks; mag = 10^floor(log10(raw)); step = first of nice_steps x mag >= raw; top = ceil(max / step) x step.
No randomness, no timestamps, no environment-dependent values, ever. Deterministic layout algorithms are part of the spec (squarified treemap, first-free-lane beeswarm packing).

What you need

File	Validates
bq.schema.json	BQ objects
ch.schema.json	CH objects
cp.schema.json	CP objects
dl.schema.json	DL objects
nr.schema.json	NR objects
rc.schema.json	RC objects
engine.json	decision rules + the controlled vocabularies
REGISTRY.json	the machine index of every object

Golden renders and their input data live under golden/ in the repository: one folder per object, data.json plus one render per design language. They are the conformance test suite: re-render and compare bytes.

Self-test

for each golden folder:
    output = render(spec, tokens[dl], data)
    assert output == stored_golden_bytes   # svg: byte-identical

The reference gate (tools/validate.py) also checks schema validity, hex discipline (#RRGGBB uppercase only, in tokens only), WCAG AA contrast for ink and body on background, and per-chart data sanity (waterfalls reconcile, cumulative curves never decrease, rank columns are permutations, five-number summaries are ordered).