Web Service as source in IDT (Joins in dfx) ?

Hi Experts,

I hope this is a proper forum for my Question!!!

We have created Universe on top of SOAP Web Services(without any prompts).

Now we have to join two different Web Service tables in Data foundation.I get an error that It is "not supported"

Any workaround in BI?

or

We must change Web Services?

Any suggestions would be helpful.

Regards,

Nouman