about implement "folder" with nanning-aop

hi all,

Recently, i am very interesting to convert some
oo-design to aop-design with nanning. so , i try to 
implement "folder" with nanning.

normally under oo design:
 Folder -extends-> FolderItem

when i use aop to design this:
  Folder -extends-> FolderItem
    |                    |
  FolderImpl -extends-> FolderItemImpl

FolderItem like a leaf, so i add class-level-tag
"nodechild"
Folder like a container, so i add class-level-tag
"nodeparent", and more, Folder is a FolderItem, so
Folder inherited attribute "nodechild" , cool!

also, i design the introductions "NodeChild" and 
"NodeParent", i think they are very general for
other object to use.

all source code and test case in the attached file 
"folder.zip".

how do you think about my design? any comments?
Thanks for your reply!

wang yiming
2003.6.20

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