par Hidders, Jan;Fletcher, George;Picalausa, Francois 
;Vansummeren, Stijn
Référence Proceedings of the 17th International Conference on Database Theory, ICDT 2014, OpenProceedings.org, page (245-256)
Publication Publié, 2014
;Vansummeren, Stijn Référence Proceedings of the 17th International Conference on Database Theory, ICDT 2014, OpenProceedings.org, page (245-256)
Publication Publié, 2014
Publication dans des actes
| Résumé : | We present a new structural characterization of the expressive power of the acyclic conjunctive queries in terms of guarded simulations, and give a finite preservation theorem for the guarded simulation invariant fragment of first order logic.We discuss the relevance of these results as a formal basis for constructing so-called guarded structural indexes. Structural indexes were first proposed in the context of semi-structured query languages and later successfully applied as an XML indexation mechanism for XPath-like queries on trees and graphs. Guarded structural indexes provide a generalization of structural indexes from graph databases to relational databases. |
