BusinessRuleTask fails to build kbase if implementation="Java" since RHDM/RHPAM 7. On the other hand, it didn't fail in BRMS 6. It was introduced by JBPM-5681 which makes validator stricter. So need to mention it in Migration guide.
"4.3. Logic changes in Red Hat Decision Manager 7.1" looks to be an appropriate section.
Suggestion:
- Since RHDM/RHPAM 7, Business Rule Task's validation is stricter so kbase build would fail if it has implementation="Java" which was overlooked in BRMS 6. To solve it, you need to set "##unspecified" as its value or remove "implementation" attribute.