XML file for domain configuration (as an alternative to domain class annotations) to externalize that configuration

There is a configuration stuff being specified by annotations on domain entities like @PlanningVariable, @PlanningEntity and so on. This configuration could be all placed in some xml file (referenced from solverConfig.xml) so that user can choose configuration style he likes.

original use case: comparing several configurations without having duplication of domain entities

Of course, anything that is exposed in the XML is also exposed in the programmatic Config.java API too.