| UB-tree | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
 Two dimensional Z-order | ||||||||||||
| Type | tree | |||||||||||
| Invented by | Rudolf Bayer and Volker Markl | |||||||||||
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The UB-tree, also known as the Universal B-Tree [1] , as proposed by Rudolf Bayer and Volker Markl is a balanced tree for storing and efficiently retrieving multidimensional data. Like a B+ tree, information is stored only in the leaves. Records are stored according to Z-order, also called Morton order. Z-order is calculated by bitwise interlacing of the keys.
Insertion, deletion, and point query are done as with ordinary B+ trees. To perform range searches in multidimensional point data, however, an algorithm must be provided for calculating, from a point encountered in the data base, the next Z-value which is in the multidimensional search range.
The original algorithm to solve this key problem was exponential with the dimensionality and thus not feasible [2] ("GetNextZ-address"). A solution to this "crucial part of the UB-tree range query" has been described later. [3] This method has already been described in an older paper [4] where using Z-order with search trees has first been proposed.
