{
  "version": "spy-share-flow-contract-v1",
  "recommended_name": "SPY净份额变化按当日净值计价的申赎代理",
  "formula": "(shares_t - split_ratio_new_per_old_t * shares_previous) * nav_t",
  "units": "USD equivalent of net units at end-of-day NAV; positive net creations, negative net redemptions",
  "required_fields": [
    "session_date",
    "NAV_unadjusted_per_current_unit",
    "shares_outstanding_same_unit_basis",
    "total_net_assets",
    "ETF_share_split_ratio",
    "observed_at_utc",
    "source_hash",
    "revision_id"
  ],
  "adjustment_rule": "Use contemporaneous raw share counts and NAV; adjust only prior share count for actual ETF unit splits. Do not use dividend-adjusted NAV or underlying-company stock splits.",
  "validation": [
    "NAV * shares reconciles to net assets within published rounding",
    "Contiguous relevant sessions; no forward filling missing shares",
    "Corporate action and merger screen, unexplained share jumps held",
    "Publication/revision timestamps retained separately from session dates"
  ],
  "usable_now": [
    "Small-window retrospective arithmetic comparison",
    "Measurement-design research before return-prediction claims"
  ],
  "not_usable_now": [
    "2003-2026 historical timing backtest",
    "Same-day close or next-day trading assumptions without observation/publication evidence",
    "Whole-market fund flows",
    "Cash-only subscriptions; primary creations can be in-kind",
    "Gross creations and redemptions inferred from net change"
  ],
  "timing_policy": "Historical publication_at is unknown: block historical tradable-signal use. In a later explicitly authorized observation run, first_observed_at and immutable revisions must gate use; merely shifting dates by one day does not establish past availability.",
  "future_revisions": "Append new versions and diff; never overwrite sealed snapshot. No automated polling authorized.",
  "recommended_next": "2号 may evaluate measurement interpretation using this isolated window; price/risk-budget research continues independently. Before timing tests, obtain observable vintages and independently confirm ETF-level actions.",
  "production_approved": false
}