I think you are both right. IMHO, a B-tree is a structure, but generally it's more of a meta structure. When you are doing something with a B-tree, you genera

I think you are both right. IMHO, a B-tree is a structure, but generally it's more of a meta structure. When you are doing something with a B-tree, you generally care about the contents of the tree, not the actual tree. The tree just happens to be the facility to efficiently manipulate the information that you really care about. Also IMHO, code is data as well. So the definition of the b-tree operations (algorithms), the tree that they operate on, and the application data within the tree are all just data (some of them just happen to have a more direct effect on run time operations).