Definition of NSA-DEVS

• Atomic model:
  • definition
    • 

    • X	set of input ports (with names)
      Y	set of output ports (with names)
      S	set of internal states
      τ	input delay, always > 0 (usually infinitesimal)
      ta(s)	lifetime of a state, always > 0
      λ(s,e,x)	output at state s, elapsed time e and input x
      δ(s,e,x)	new state at state s, elapsed time e and input x

• Differences to PDEVS:
  • input and output use ports with names instead of bags
    • trivial, but useful in practice
  • based on RPDEVS, i.e.
    • only one transition function δ(s, e, x)
    • only one output function λ(s, e, x)
  • use hyperreal numbers a + b ε with infinitesimal ε
  • input delay time τ > 0
    • external event at t → call of λ and δ at t + τ
    • internal event at t → call of λ and δ at t
  • lifetime ta(s) of a state always > 0 (may be infinitesimal)
• Coupled model:
  • set of lists
    • submodels (atomic or coupled)
    • input and output ports
    • connections between submodels
    • connections from or to the external ports
  • no additional delays at input ports
• Abstract Simulator:
  • describes the execution of a specified model
  • basic structure identical to PDEVS simulator
    • modules root coordinator, coordinator and simulator
    • hierarchical structure representing the model structure (coupled/atomic)
    • different messages between modules implement behaviour
  • Mealy behaviour and input delays are implemented in messages