@inproceedings{e6cd0bbc8c7b43849cf71f2775d05149,
title = "Query Answering under Expressive Entity-Relationship Schemata",
abstract = "We address the problem of answering conjunctive queries under constraints representing schemata expressed in an extended version of the Entity- Relationship model. This extended model, called ER + model, comprises is-a constraints among entities and relationships, plus functional and mandatory participation constraints. In particular, it allows arbitrary permutations of the roles in is-a among relationships. A key notion that ensures high tractability in ER + schemata is separability, i.e., the absence of interaction between the functional participation constraints and the other constructs of ER + .We provide a precise syntactic characterization of separable ER + schemata, called ER± schemata, by means of a necessary and sufficient condition. We present a complete complexity analysis of the conjunctive query answering problem under ER± schemata. We show that the addition of so-called negative constraints does not increase the complexity of query answering. With such constraints, our model properly generalizes the most widely-adopted tractable ontology languages.",
author = "Andrea Cal{\`i} and Georg Gottlob and Andreas Pieris",
year = "2010",
doi = "10.1007/978-3-642-16373-9_25",
language = "English",
isbn = "978-3-642-16372-2",
series = "Lecture Notes in Computer Science (LNCS)",
publisher = "Springer",
pages = "347--361",
booktitle = "Conceptual Modeling - ER 2010, 29th International Conference on Conceptual Modeling, Vancouver, BC, Canada, November 1-4, 2010. Proceedings",
address = "United Kingdom",
}