Indexing Type Hierarchies with Multikey Structures

(extended abstract) Thomas A. Mueck Martin L. Polaschek Abteilung f ur Data Engineering Universitat Wien fmueck, [email protected] Abstract Multikey index structures for type hierarchies are a recent alternative to traditional B+-tree based proposals. A prerequisite for the e cient use of multikey structures in this eld is an appropriate linearization of the type hierarchy. We present the relevant problem description, i.e., the de nition of an optimal hierarchy linearization, and an algorithm which is able to map type hierarchies to linear ordered attribute domains in such a way that each subhierachy is represented by an interval of this domain. The mapping is straightforward for single inheritance hierarchies but less obvious in case of multiple inheritance. Based on an example, it is argued that this kind of hierarchy-to-domain mapping yields a signi cant query performance enhancement in a multikey type index.