As you are not generating Code from it and you are using it only for impact lineage (as we do also for
importet and automatically matched objects from informatica), why you care about any operations then ?
If table1.a = table2.a + table3.b
then just generate mappings
table1.a --> table2.a
table1.a --> table3.b
IMHO the documentation facilities of most ETL tools are much more powerful as what you can get with PD in this case
dj