The model contains one compartment called C. There are four species called S1, S2, S3 and S4 and one parameter called k1. The model contains three reactions defined as:

Reaction Rate
S1 + S2 → S3 k1 · S1 · S2 · C · s
S3 → S1 + S2 k1 · S3 · C · s
S3 → S1 + S4 k1 · S3 · C · s

where the symbol 's' denotes the current simulation time.

Both reactions S3 → S1 + S2 and S3 → S1 + S4 define a local parameters k1 which has a scope local to the defining reaction and are different from each other and the global parameter k1 used in the reaction S1 + S2 → S3.

The initial conditions are as follows:

Value Units
Initial amount of S1 2.0 mole
Initial amount of S2 2.0 mole
Initial amount of S3 0 mole
Initial amount of S4 0 mole
Value of parameter k1 1.0 litre mole-1 second-2
Value of local parameter k1 (R2) 0.9 second-2
Value of local parameter k1 (R3) 0.7 second-2
Volume of compartment C 1 litre

The species values are given as amounts of substance to make it easier to use the model in a discrete stochastic simulator, but (as per usual SBML principles) their symbols represent their values in concentration units where they appear in expressions.