It is not possible to combine questions from any namespace with questions from any namespace in a single calculation query.

It is allowed to combine only questions from a recontact namespace with questions from its parent_namespace_code. This compatibility is for indefinite recontact parent relationship, i.e. recontact can be combined with its parent_namespace_code and with the parent_namespace_code of the parent_namespace_code, etc.

For example, assume the below namespaces:

"code": "core", "type": "fresh", "parent_namespace_code":null
"code": "gwi-r1", "type": "recontact", "parent_namespace_code": "core"
"code": "gwi-r2", "type": "recontact", "parent_namespace_code": "gwi-r1"
"code": "gwi-r3", "type": "recontact", "parent_namespace_code": "gwi-r2"
"code": "gwi-r10", "type": "recontact", "parent_namespace_code": "core"

In the above example questions from namespaces core, gwi-r1, gwi-r2 and gwi-r3 can be freely combined in a single calculation query because there is a parent child relationship among all of them.

It is also possible to combine in a single calculation query questions from namespaces core and gwi-r10 because there is a parent child relationship between them.

However, it is not allowed to combine in a single calculation query questions from gwi-r10 with questions from namespaces gwi-r1 or gwi-r2 or gwi-r3 because there is not a parent child relationship between the gwi-r10 namespace and the other namespaces.