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

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

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

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

Trigger Delay Assignments
Event1 S1 < 0.75 0.7 S2 = 1.5
S1 = 1

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 local parameter k 0.75 litre mole-1 second-1
Value of local parameter k 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.