Program rule engine
The program rule engine is not provided within the SDK. It is implemented in a separate library, so the same code is used by backend and android apps.
info
The DHIS2 Android SDK and the Program Rule Engine use a common library to parse the DHIS2 expressions, the DHIS2 Antlr Expression Parser. If the application imports both the the SDK and the Rule Engine, it is important that their parser versions match exactly; otherwise it could cause an unexpected behavior in the evaluation. Check compatibility table here.
More info dhis2-rule-engine.