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This article is about a tree data structure for storing data in multiple dimensions. For the XTree file manager, see XTree.

In computer science, an X-tree is an index tree structure based on the R-tree used for storing data in many dimensions. It differs from R-trees, R+-trees and R*-trees because it emphasizes prevention of overlap in the bounding boxes, which increasingly becomes a problem in high dimensions. In cases where nodes cannot be split without preventing overlap, the node split will be deferred, resulting in super-nodes. In extreme cases, the tree will linearize, which defends against worst-case behaviors observed in some other data structures.


Berchtold, Stefan; Keim, Daniel A.; Kriegel, Hans-Peter (1996). "The X-tree: An Index Structure for High-Dimensional Data". Proceedings of the 22nd VLDB Conference (Mumbai, India): 28–39.