Figure 1: Example of R-tree indexing structure
The R-tree indexing structure is basically constructed of a number of multi-dimensional rectangles, and is balanced dynamically with all the data objects stored in the same level. Each rectangle in the higher level is formed by enclosing multiple child rectangles from a lower level. At the bottom level (Leaf-level), each MBR is generated by enclosing data objects. Each node in the Leaf-level or non-Leaf level is allowed to have a number of children between upper-bound and lower-bound values. There is no minimum number of children required in the root level. The root node can store any number of children up to the maximum child allowance.