In addition to expressions and quantities, which are model components, SimBiology® provides the following constructs (or objects) that you use to modify or perturb a model from its base configuration.
A variants is a collection of quantities (compartments, species, and/or parameters) that you can use to alter a model's initial or base configuration, which is easier than individually modifying each quantity separately. For example, assuming that a different set of parameter values characterizes differences between wild type and mutant strains, you can use a variant to group parameter values indicative of these strains. You apply variants to a model to evaluate the model behavior under "variant" conditions. Note that the model's original configuration is only temporarily altered, for example during a simulation.
For example, you can use a variant to compare:
Two different species, such as human versus mouse
Wild type versus mutant strains
Different experimental conditions
A dose is used to increment the amount (or concentration) of a species exogenously. For example, you can use a dose to model the instantaneous supply of a drug regimen during the simulation of a model.