The Data Model: Elements (2/2)

• Properties of elements - represented as interfaces
  
  

  Elements and Their Properties

  Property	Signal	Track	Switch	Goal	Values
  Indication	yes	no	no	no	halt, clear
  Lock	yes	no	yes	yes	true, false
  Interdiction	no	yes	yes	no	true, false
  Position	no	no	yes	no	left, right,...
  Track circut	no	yes	yes	no	free, occupied
  Fault	yes	no	yes	no	true, false