# The PN-Tree: A Parallel and Distributed Multidimensional Index

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## Abstract

Multidimensional indexing is concerned with the indexing of multi-attributed records, where queries can be applied on some or all of the attributes. Indexing multi-attributed records is referred to by the term *multidimensional indexing* because each record is viewed as a point in a multidimensional space with a number of dimensions that is equal to the number of attributes. The values of the point coordinates along each dimension are equivalent to the values of the corresponding attributes. In this paper, the *PN-tree*, a new index structure for multidimensional spaces, is presented. This index structure is an efficient structure for indexing multidimensional points and is parallel by nature. Moreover, the proposed index structure does not lose its efficiency if it is serially processed or if it is processed using a small number of processors. The *PN-tree* can take advantage of as many processors as the dimensionality of the space. The *PN-tree* makes use of B^{+}-trees that have been developed and tested over years in many DBMSs. The *PN-tree* is compared to the *Hybrid tree* that is known for its superiority among various index structures. Experimental results show that parallel processing of the *PN-tree* reduces significantly the number of disk accesses involved in the search operation. Even in its serial case, the *PN-tree* outperforms the *Hybrid tree* for large database sizes.

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