The REST API kept full backward compatibility to 0.8.0
Bindings implemented against 0.8.0 should be source compatible to this release. Nevertheless, the APIs have evolved and a few methods and services have been marked as deprecated. Implementors are therefore asked to check their implementation against the updated APIs and adapt them to the newer version (dedicated information on how to do so is given on every deprecation notice).
The new rule engine (previously marked as experimental only) has matured and while the APIs are still fairly similar, its general behavior might have changed through a different runtime behavior. Implementors should therefore check and update their code.
Version 0.9.0 has dropped support for Java 7 - Java SE 8 Compact Profile 2 is now the minimal system requirement.