With a ReadVariable Action, usually used in combination with a WriteVariable Action you can read the value of a previously defined variable via object flows.
The ReadVariable Action will simmilar to the Primitve Types and the ValueSpecification Action simply us the name (not normalized) provided in he model to generate code.
This will give you enormouse flexibility reading modeled data. For a more strict approach reading model data you can also use a ReadStructuralFeature Action (since version 3.3).
In the sample shown below the ReadVariable Action was not only used to read a variable... but to read and add two variables at the same time.