Hi
Im trying to answer ur first question.Ofcource it is my own analysis.
when u implement marker interfaces, JVM will come to know that this class is having this particular facility like serializable etc..
JVM has developped like that as they(sun people) know all marker interface when they r developping JVM.And we can not develop marker interfaces,y bcoz we can not change the JVM functionality.so Developping marker interfaces is reserved to sun systems only.
I think I answered ur question.I tried to say what I know abt marker interfaces.
I didn't get ur point clearly in ur second question??