Abstract
Expressive Description Logics (DLs) have been advocated as formalisms for modeling the domain of interest in various application areas. An important requirement is the ability to answer complex queries beyond instance retrieval, taking into account constraints expressed in a knowledge base. We consider this task for positive existential path queries (which generalize conjunctive queries and unions thereof), whose atoms are regular expressions over the roles (and concepts) of a knowledge base in the expressive DL ALCQIbreg . Using techniques based on two-way tree-automata, we first provide an elegant characterization of TBox and ABox reasoning, which gives us also a tight EXPTIME bound. We then prove decidability (more precisely, a 2EXPTIME upper bound) of query answering, thus significantly pushing the decidability frontier, both with respect to the query language and the considered DL. We also show that query answering is EXPSPACE-hard already in rather restricted settings.

URL:
http://rewerse.net/publications/rewerse-publications.html#REWERSE-RP-2007-139

BibTeX:

@inproceedings{REWERSE-RP-2007-139,
	author = {Diego Calvanese and Thomas Eiter and Magdalena Ortiz},
	title = {Answering Regular Path Queries in Expressive Description Logics: An Automata-Theoretic Approach},
	booktitle = {Proceedings of Twenty-Second AAAI Conference on Artificial Intelligence, Vancouver, British Columbia (22nd July--26th February 2007)},
	year = {2007},
	organization = {AAAI},
	pages = {391--396},
	url = {http://rewerse.net/publications/rewerse-publications.html#REWERSE-RP-2007-139}
}