To access steps inputs and calculation outputs, you can use:
model.inputs(String stepName, String tabName)
model.outputs(String stepName, String calculationName)
Also api.input(String inputName)
can be used to access the current tab inputs.
A logic being executed in the context of a given step is only able to access previous steps inputs as well as previous calculations outputs
A tab cannot access inputs from other tabs of the same step.