Suppose we have
- N species: X_1, X_2, \ldots, X_N
- M reactions: R_1, R_2, \ldots, R_M
- In a typical model, M = 2N
Reaction R_i takes the form \begin{array}{cccc} R_{i}: \, & u_{i1} X_1+\ldots +u_{ik} X_N &\xrightarrow {\phantom{a}c_{i}\phantom{a}} & v_{i1}X_1+\ldots +v_{ik}X_N \end{array} The effect of reaction i on species j is to change X_j by an amount v_{ij} - u_{ij}
- Straightforward to simulate