The model contains one compartment called C. There are three species called S1, S2 and S3 and two parameters called k1 and k2. 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 two events that assign values to species S2 and S1:

Trigger Delay Assignments
Event1 lessthan(S1, 0.7) S2 = 1.5
S1 = 1

The event trigger uses the functionDefinition defined as:

Id Arguments Formula
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
Value of parameter k1 0.75 litre mole-1 second-1
Value of parameter k2 0.25 second-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.