Need help urgently...please

How does one export and later import in another d/b a schema containing object types. Is it possible to "take along" all the objects (attributes and methods) and the underlying tables etc... ? I am having all kinds of problems because some of the attributes in some objects ref other objects.

If I need to change an object's definition (say add an attribute) in my case I have to drop all the underlying tables first and then delete objects that are being refed before I can add an attribute.

Am I doing something wrong, or have I overlooked some thing.

Thanks in advance for all the help.

Mohd.