If you have defined a soap or rest service within your GeneXus 16u5 Knowledge Base, can you then create an external object for that service and invoke it from within the same KB?
I seem to remember in the past that this was not possible. If it is still the case, is it because of the tools that generate the external object?
Sure you can, it's not common but you have to be careful with the externals objects names. To avoid errors during the WSDL import, in the second step you've to:
1- Change the name of the "External Name Object" to something different of the "internal" object.
2- Keep or put something in the Prefix box. If you leave it blank, a conflict with the "internal" SDT will occur.
Regarding REST, I always consume them in a manually way, so I guess there would be no problem doing it that way.