The model contains one compartment called C. There are two species called S1 and S2 and two parameters called kf and kr. The model contains two reactions defined as:

Reaction Rate
S1 ↔ S2 (kf · S1 − kr · S2) · C
S3 ↔ S4 (kf · S3 − kr · S4) · C

Reaction S1 ↔ S2 defines two local parameters kf and kr which have a scope local to the defining reaction and are different from the global parameters kf and kr used in the Reaction S3 ↔ S4.

The initial conditions are as follows:

Value Units
Initial amount of S1 1.0 mole
Initial amount of S2 0 mole
Value of parameter kf 0.9 second-1
Value of parameter kr 0.075 second-1
Value of local parameter kf 0.8 second-1
Value of local parameter kr 0.06 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.