The model contains one compartment called C. There are four species called S1, S2, S3 and S4 and four parameters called k1, k2, k3 and k4. The model contains two reactions defined as:

Reaction Rate
S1 + S2 → S3 k1 · S1 · S2 · C
S3 → S1 + S2 k2 · S3 · C

The model contains one rule that determines the rate at which species S4 is changing:

Type Variable Formula
Rate S4 k2 · add(S1, S2)

The model contains one event that assign values to species S2 and S4:

Trigger Delay Assignments
Event1 lessthan(S1, 0.6) S2 = 1
S4 = add(k3, k4)

Both the event trigger and assignment and the rateRule use functionDefinitions defined as:

Id Arguments Formula add x, y x + y
lessthan x, y x < y

The initial conditions are as follows:

Value Units
Initial amount of S1 1.0 mole
Initial amount of S2 2.0 mole
Initial amount of S3 1.0 mole
Initial amount of S4 1.5 mole
Value of parameter k1 0.75 litre mole-1 second-1
Value of parameter k2 0.25 second-1
Value of parameter k3 0.5 mole litre-1
Value of parameter k4 0.5 mole litre-1
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.