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.

https://access.redhat.com/documentation/en-us/red_hat_decision_manager/7.1/html-single/migrating_from_red_hat_jboss_brms_6.4_to_red_hat_decision_manager_7.1/#migration-other-changes-con

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.