{
  "observation_sources.csv": {
    "fields": {
      "observation_id": "Observation foreign key.",
      "source_id": "Source foreign key.",
      "source_role": "primary for the lead cited evidence; supporting for additional corroboration. This is distinct from source_tier."
    },
    "foreign_keys": {
      "observation_id": "observations.csv",
      "source_id": "sources.csv"
    },
    "primary_key": [
      "observation_id",
      "source_id"
    ]
  },
  "observations.csv": {
    "fields": {
      "category": "passenger_fare, vehicle_cost, or unit_economics.",
      "currency": "ISO 4217 currency code, if applicable.",
      "date_precision": "year, month, or day; prevents false date precision.",
      "description": "Concise description mapped from the source JSON.",
      "geography": "Geographic scope stated by the source data.",
      "observation_date": "Source date retained at its published precision (YYYY, YYYY-MM, or YYYY-MM-DD).",
      "observation_id": "Stable, human-readable observation identifier.",
      "observation_type": "The evidence shape, such as sample_average or pricing_event.",
      "scope_note": "Interpretation limit that must accompany the observation.",
      "service": "Operator, benchmark, vehicle, or metric label.",
      "source_data_paths": "Pipe-separated source JSON paths merged into this observation.",
      "value_max": "Normalized upper bound when the claim is a range.",
      "value_min": "Normalized lower bound when the claim is a range.",
      "value_numeric": "Single normalized numeric value when the claim supports one.",
      "value_text": "Lossless human-readable representation of the claim.",
      "value_unit": "Unit for numeric fields or the kind of non-scalar value."
    },
    "primary_key": "observation_id"
  },
  "sources.csv": {
    "fields": {
      "name": "Publisher or source label used by the site.",
      "source_id": "Stable SHA-256-derived identifier based only on the source URL.",
      "source_tier": "Editorial evidence tier: primary, research, secondary, or estimate.",
      "url": "Specific HTTPS source URL."
    },
    "primary_key": "source_id"
  }
}