Hi Net, The RMI vs Serialized objects over sockets question comes up quite often. Try doing a search in this forum with "RMI Serialized" as your keywords. You will find plenty of really good explanations of what the issues are. I think the extending Data vs modifying comes down to a few things:
is the original programmer likely to change the Data class? If so, you probably want to extend rather than modify, otherwise either your code changes or theirs will be lost.
do you have any extra functionalitly that you want to add? Given that we are told that the classes provided are complete with the exception of three methods, you might not want to add any extra functionality - your choice.
given that the code has to be understandable by a junior programmer, do you want them to be able to find all the code in one class, or should they have to look in the base class and the extended class? what is easier for them to understand?
Anyone care to add some more issues for the extendsion vs modification question? Regards, Andrew