# Relationship history for MSHA mine 4003031

Current hierarchy: **John H  Ford → Ford Construction Company → Langley-Curve Pit**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** John H  Ford  et al → Langley-Curve Pit; 1985-08-21 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Ford Construction Company → Langley-Curve Pit; 1990-05-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** John H  Ford  et al → Ford Construction Company; 1990-05-01 to current/open; source msha-controller-operator-history