A Declarative DSL

Surprise: A single rule is sufficient if the test algorithms are shunted into the respective subclasses of Check:

rule "All checks"
when
    $fact: Object()
    $cond: Check( clazz == ( $fact.getClass() ) )
    eval( ! $cond.isValid( $fact ) )
then
    System.out.println( $cond.getError() + " " + $fact.toString() );
end