R2RML: classes of triples map only constants

Hello,

During the last couple of days, I started and sort of finished some kind of
r2rml representation in Python. I can't say it is an exact r2rml processor
implementation. However, I tried to follow the r2rml document during design.
Disclaimer: I am not a programmer by profession.

Something I have noticed: is that the RDF types of a triples map (the
"classes"), can only be constants.

What happens in the scenario where you want a dynamic class, for example
column-based. Take this scenario:

Table Employees:
Emp_ID: 1234
EMP_Name: "John Smith"
EMP_Pay: "PartTimeEmployee"

You want to assign the triples map two classes: one is Employee (constant)
and the other is PartTimeEmployee (derived from a column).

So I was wondering if you did not have this scenario in mind, or was the
design intentional with a dynamic RDFtype assigned only through a separate
predicate-object map??

Cheers,
Ahmed Bassiouni