[tcbawo]

Unique pointers imply ownership of the underlying memory. If you have multiple references to the same data, or in your case a tree, it might make sense to use raw pointers (or references) to access the tree data. It would not make sense to grant ownership of the same memory to two unique_ptr, or make copies of data unnecessarily.

[inetknght]

In that case, you'd have something like `std::vector` or `std::unique_ptr` which owns the actual allocation (and governs the scoping and therefore deallocation), while using `vector.data()` or `unique_ptr.get()` to pass around an unowned pointer. All raw pointers can then be considered to be unowned by convention.