Behaviors of a given DEVS model is a set of sequences of timed events including null events, called event segments which make the model move one state to another within a set of legal states. To define this way, the concept of a set of illegal state as well a set of legal states are needed to be introduced.
Contents
- View 1 total states states elapsed times
- View 2 total states states lifespans elapsed times
- Features of View1
- Features of View2
- References
In addition, since the behaviors of a given DEVS model needs to define how the state transition change both when time is passed by and when an event occurs, it has been described by a much general formalism, called general system [ZPK00]. In this article, we use a sub-class of General System formalism, called timed event system instead.
Depending on how to define the total state and its external state transition function of DEVS, two ways to define the behavior of a DEVS model using Timed Event System. Since behavior of a coupled DEVS model is defined as an atomic DEVS model, behavior of coupled DEVS class is defined by timed event system.
View 1: total states = states * elapsed times
Suppose that a DEVS model,
- the external state transition
δ e x t : Q × X → S . - the total state set
Q = { ( s , t e ) | s ∈ S , t e ∈ ( T ∩ [ 0 , t a ( s ) ] ) } wheret e T = [ 0 , ∞ ) denotes the set of non-negative real numbers, and
Then the DEVS model,
For a total state
If unit event segment
If unit event segment
If unit event segment
Computer algorithms to simulate this view of behavior are available at Simulation Algorithms for Atomic DEVS.
View 2: total states = states * lifespans * elapsed times
Suppose that a DEVS model,
- the total state set
Q = { ( s , t s , t e ) | s ∈ S , t s ∈ T ∞ , t e ∈ ( T ∩ [ 0 , t s ] ) } wheret s s ,t e t s T ∞ = [ 0 , ∞ ) ∪ { ∞ } denotes the set of non-negative real numbers plus infinity, - the external state transition is
δ e x t : Q × X → S × { 0 , 1 } .
Then the DEVS
For a total state
If unit event segment
If unit event segment
If unit event segment
Computer algorithms to simulate this view of behavior are available at Simulation Algorithms for Atomic DEVS.
Features of View1
View1 has been introduced by Zeigler [Zeigler84] in which given a total state
where
When a DEVS model receives an input event
in the external state transition function
Since the number of possible values of
If we don't care the finite-vertex reachability graph of a DEVS model, View1 has an advantage of simplicity for treating the elapsed time
Features of View2
View2 has been introduced by Hwang and Zeigler[HZ06][HZ07] in which given a total state
When a DEVS model receives an input event
Unlike View1, since the remaining time