Superprocess A sets variable V to value "foo".
Superprocess A calls subprocess B (A passes variable V to B with acces READ and WRITE).
Subprocess B sets variable V to #

{null}.
Subprocess B finishes.
Superprocess checks value of V - it is equal "foo".

Expected behaviour:
value of V equal #{null}

in superprocess A after execution of subprocess B.

This is becouse in ProcessState.java in methods execute and leave there is check:

if (value!=null) {
//pass variable etc etc ..

This check can be removed and jbpm behaves as it should (I've checked in version 3.2.7 from svn).

But - I've found this thread - http://www.jboss.org/index.html?module=bb&op=viewtopic&t=73339 - it says this check is to not throw NullPointer exception when process has out variable that it doesn't write to it.

I've checked this situation with fixed version, and it don't throw exceptions, but maybe I'm missing something.