Abstract Class:Abstract class is rule created to supported the defination of rule,including other classes such rules can be inherited  by sub class of the abstract class rules with a class as akey part such as properties, activitys flows and models ...

it does end with "-"symbol

concrete class: A class that is not a abstract concrete class unlike abstract classes ,concrete class can have instances stored in the databases
selection of the class rule fom determine weather a abstract or concrete

concrete class doesn't have "-"symbol


concrete class nothing but a classgroup.