#gas_system__gassystem  facility (plant and equipment) for providing natural-gas service
  supertype:  installation__facility  a building or place that provides a particular service or is used for a particular industry; "the assembly plant is an enormous facility"
  part of:  infrastructure
  part:  gas_main__gasmain  a main that distributes gas

No statement uses or specializes gas_system; click here to add one.