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

Reaction Rate
S1 + S2 → S3 + S4 k · S1 · S2 · C
S3 + S4 → S1 + S2 k · S3 · S4 · C

Reaction S1 + S2 → S3 + S4 defines one local parameter k. Reaction S3 + S4 → S1 + S2 defines another (different) local parameter k. Note that these parameters have a scope local to the defining reaction.

The model contains two events that assign value to species S1 and S4:

?(t_c)
Trigger Delay Assignments
Event1 S4 > S2 1.5 S1 → 2 × 10−4
Event2 S3 > 2.25 × 10−4 0.5 S4 → 1 × 10−4

The initial conditions are as follows:

Value Units
Initial amount of S1 1.0 × 10−4 mole
Initial amount of S2 1.0 × 10−4 mole
Initial amount of S3 2.0 × 10−4 mole
Initial amount of S4 1.0 × 10−4 mole
Value of local parameter k 0.75 × 104 litre mole-1 second-1
Value of local parameter k 0.25 × 104 litre mole-1 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.