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

Reaction Rate
S1 → S2 k1 · S1 · C
S2 → S3 k2 · S2 · C
S3 → S1 k3 · S3 · C

The model contains one event that assigns values to both species S1 and S2:

Trigger Delay Assignments
Event1 S1 < 0.75 S2 = 1.5
S1 = S2

Note that the event assignments should happen simultaneously, not sequentially; i.e., the value of S2 assigned to S1 is the value at the point at which the event was triggered.

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 second-1
Value of parameter k2 0.55 second-1
Value of parameter k3 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.