## DEVS

DEVS is a recognised formalism for specifying complex discrete or continuous systems. This formalism is represented by a network of atomic and coupled models, interacting and competing over time. Atomic model DEVS defines an atomic model as a set of input and output ports, states and state transition functions. \[M = \left\langle X,Y, S, \delta_{\text{int}}, \delta_{\text{ext}}, \delta_{\text{con}},\lambda, \tau \right\rangle\] Where: \(X\) is the set of all input values \(Y\) is the set of all output values \(S\) is the set of all sequential states \(\tau: S \to \mathbb{R}_0^+\) is the time advance function \(Q = \{(s,e) | s \in S, 0 \leq e \leq \tau(s)\}\), \(Q\) is the set of total states where: \(e\) is the time since the last transition \(\delta_{\mathit{int}}: S \to S\) is the internal transition function \(\delta_{\mathit{ext}}: Q \times X^b \to S\) is the external transition function \(X^b\) is the set of values in \(X\) built at \(t\) \(\delta_{con}: S \times X^b \to S\) is the confluent function subject to \(\delta_{con}(s, \emptyset) = \delta_{\mathit{int}}(s)\) \(\lambda: S \to Y\) is the output function If no external event occurs, the system will stay in state \(s\) for \(\tau(s)\) time.