It's annoying that the user both has to declare a @PlanningSolution and implement the Solution interface. That's a ugly and inconsistent.

Some idea's how to deal with this if and only if the Solution interface isn't implemented:

• Introduce an optional method annotation @ProblemFacts.
  • If is declared, that method is the getProblemFacts() method and must return a Collection
  • If it is not declared, a reflection thing goes through all fields and adds all fields that aren't a @PlanningEntityCollectionProperty.
  • If it's declared multiple times, fail fast.
• Introduce an required field/method annotation @Score for the score field
  • If it's missing, fail fast. If it's declared multiple times, fail fast.
• If a solution class does implement the deprecated Solution interface, it all behaves backwards compatibly.