Scope: "Balls" = sport balls only (basketball, soccer, volleyball, football, baseball, softball, tennis, table tennis, golf, bowling); bats, racquets/paddles, sticks/clubs/mallets, goals/hoops/nets/posts, and protective gear are sibling catalog leaves and out of scope.

Seed:
1. Balls equivalent of harvest_date: coverstock_type (bowling) / golf_compression_feel — rarely stated plainly on a listing, decides hook or distance, needs research rather than a title field.
2. The endurance-athlete persona would clock bladder/core material first (butyl vs cheap rubber, cork-rubber vs kapok): the hidden "cost per rep" factor — a leaky bladder means re-inflating before every session, which a casual buyer never notices until it's already annoying.

Sources:
[wiki_basketball_ball] https://en.wikipedia.org/wiki/Basketball_(ball) — size 7 = 29.5–30.3in/20–22oz, butyl bladder — fetched excerpt
[wiki_basketball_general] https://en.wikipedia.org/wiki/Basketball — size 7 = 29.5in/22oz, size 6 = 28.5in/20oz — fetched excerpt
[wiki_soccer_ball] https://en.wikipedia.org/wiki/Football_(ball) — size 5 = 68–70cm/410–450g, 32-panel — fetched excerpt
[ifab_laws_of_game] https://www.theifab.com/laws/latest/the-ball/ — confirms size 5 spec and 0.6–1.1 atm — fetched excerpt
[wiki_volleyball_ball] https://en.wikipedia.org/wiki/Volleyball_(ball) — standard/youth/beach table, psi by class — fetched excerpt
[wiki_volleyball_general] https://en.wikipedia.org/wiki/Volleyball — confirms 65–67cm, 4.26–4.61 psi — fetched excerpt
[wiki_american_football_ball] https://en.wikipedia.org/wiki/American_football_(ball) — NFL 12.5–13.5psi, 14–15oz — fetched excerpt
[wiki_american_football_general] https://en.wikipedia.org/wiki/American_football — confirms psi/weight, college/HS note — fetched excerpt
[wiki_baseball_ball] https://en.wikipedia.org/wiki/Baseball_(ball) — 9–9.25in, cork/rubber core, 108 stitches — fetched excerpt
[wiki_baseball_general] https://en.wikipedia.org/wiki/Baseball — confirms ~9in, rubber/cork center, cowhide — fetched excerpt
[wiki_softball] https://en.wikipedia.org/wiki/Softball — 12in adult fastpitch, 11in youth, kapok/cork-rubber/PU core — fetched excerpt
[wiki_tennis_ball] https://en.wikipedia.org/wiki/Tennis_ball — ITF 2.57–2.70in/1.98–2.10oz, pressurized vs pressureless — fetched excerpt
[wiki_tennis_general] https://en.wikipedia.org/wiki/Tennis — confirms 2.575–2.700in/56.0–59.4g — fetched excerpt
[wiki_table_tennis_ball] https://en.wikipedia.org/wiki/Table_tennis — 40mm/2.7g poly since 2014, 1–3 star — fetched excerpt (same article as general page, single source)
[wiki_golf_ball] https://en.wikipedia.org/wiki/Golf_ball — conforming ≤45.93g/≥42.67mm, 2/3/4-piece, compression-vs-swing-speed — fetched excerpt
[wiki_golf_general] https://en.wikipedia.org/wiki/Golf — confirms USGA/R&A govern equipment, "conforming" term — fetched excerpt
[wiki_bowling_ball] https://en.wikipedia.org/wiki/Bowling_ball — USBC ≤16lb, 8.500–8.595in, coverstock hook order — fetched excerpt
[wiki_bowling_general] https://en.wikipedia.org/wiki/Ten-pin_bowling — confirms USBC diameter/weight max — fetched excerpt

Branches:
ball_family: the five families use unrelated construction (bladder, wound core, felt shell, dimpled solid, drilled coverstock), so every downstream facet depends on this answer.
team_sport_type: basketball/soccer/volleyball/football share bladder construction but each has its own size system and cover axis, named per-sport facets.
bat_ball_type: baseball vs softball share core/seam/circumference-class facets but differ in typical values, so branches ask the same three facets either way.
racquet_sport_type: tennis's pressurization and table tennis's material/star grade are mutually exclusive — each branch hides the other sport's facet.

Noise (spec-sheet rows not turned into facets):
- Golf exact weight/diameter (45.93g/42.67mm) — regulatory ceiling, not a buyer choice; kept as context text, not a dedicated numeric facet.
- Golf dimple count/pattern — unregulated range, marketing detail only; omitted.
- Exact inflation PSI per sport — folded into why_experts_care prose instead of a standalone numeric facet; buyers set pressure by pump gauge, not by a listing spec.
- Bowling RG, RG differential, coefficient of friction — too technical for a buyer-facing facet; summarized qualitatively inside bowling_coverstock_type instead.
- Price, brand, star/review rating — excluded per rule; not expertise.
- Ball color (orange basketball, optic yellow tennis/softball, white/orange table tennis) — cosmetic, not a judged spec for any of the ten types.
- Soccer youth sizes 3/4 exact circumference — no dual-sourced number found this run; kept as unsourced category values only.

Corrections (2026-10-26):
- Added facet `basketball_channel_construction` (deep/moderate/shallow channel pattern, affects grip, separate from cover material), wired into the `team_sport_type` basketball branch and every sibling branch's `makes_irrelevant`; sourced to Wilson's NBA Official Game Basketball spec sheet (new ref `wilson_nba_channel_spec`, metafield "Channel Construction: NBA Pro Seams" — fetched excerpt), flagged single-sourced via a new judgement (a second brand sheet with the same named row was blocked, 403/JS shell, this run).
- Added vocabulary entries for `ITTF`, `USBC`, and `celluloid`, each used undefined in `table_tennis_grade`/`bowling_weight` text.
- Added vocabulary entry for `Channel construction` (new term from the facet above).
- Re-fetched `ifab_laws_of_game` with a browser user-agent (`curl -A "Mozilla/5.0"`); the Gatsby SSR page now returns the full rule text ("circumference of between 68 cm... and 70 cm", "410 g... and 450 g") — confirms the dual-source citation on `soccer_ball_size` was correct; no JSON change needed, citation re-verified.
- Changed `tennis_pressurization.source` from `researched` to `listing`: its own `listing_field_hint` already says the keyword is usually in the title/description, matching this register's own definition of `source: listing`.