# Relationship history for MSHA mine 4703025

Current hierarchy: **Karen  Taff → Madison Sand & Gravel Company Inc → PORTABLE SCREENING PLANT**

- 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:** Calvin R  Ziegler → PORTABLE SCREENING PLANT; 1950-01-01 to 2015-03-03; source msha-controller-operator-history
- **operator_operates_mine:** Madison Sand & Gravel Company Inc → PORTABLE SCREENING PLANT; 1994-06-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Calvin R  Ziegler → Madison Sand & Gravel Company Inc; 1994-06-01 to 2015-03-03; source msha-controller-operator-history
- **controller_controls_mine:** Karen  Taff → PORTABLE SCREENING PLANT; 2015-03-04 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Karen  Taff → Madison Sand & Gravel Company Inc; 2015-03-04 to current/open; source msha-controller-operator-history