XML query languages need to provide some mechanism to inspect and manipulate nodes at all levels of an input tree. In this paper we investigate the expressive power provided in this regard by structural recursion. We show that the combination of vertical recursion down a tree combined with horizontal recursion across a list of trees gives rise to a robust class of transformations: it captures the class of all primitive recursive queries. Since queries are expected to be computable in at most polynomial time for all practical purposes, we next identify a restriction of structural recursion that captures the polynomial time queries. Although this restriction is semantical in nature, and therefore undecid-able, we provide an effective syntax. We also give corresponding results for list-based complex objects. © Springer-Verlag Berlin Heidelberg 2007.
CITATION STYLE
Robertson, E. L., Saxton, L. V., Van Gucht, D., & Vansummeren, S. (2006). Structural recursion on ordered trees and list-based complex objects: Expressiveness and PTIME restrictions. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 4353 LNCS, pp. 344–358). https://doi.org/10.1007/11965893_24
Mendeley helps you to discover research relevant for your work.