Learn More
A consistent query answer in a possibly inconsistent database is an answer which is true in every (minimal) repair of the database. We present here a practical framework for computing consistent query answers for large, possibly inconsistent relational databases. We consider relational algebra queries without projection, and denial constraints. Because our(More)
The framework of consistent query answers and repairs has been introduced to alleviate the impact of inconsistent data on the answers to a query. A repair is a minimally different consistent instance and an answer is consistent if it is present in every repair. In this article we study the complexity of consistent query answers and repair checking in the(More)
We study normalization of deterministic sequential top-down tree-to-word transducers (stws), that capture the class of deterministic top-down nested-word to word transducers. We identify the subclass of earliest stws (estws) that yield normal forms when minimized. The main result of this paper is an effective normalization procedure for stws. It consists of(More)
We study here the impact of priorities on conflict resolution in inconsistent relational databases. We extend the framework of [1], which is based on the notions of repair and consistent query answer. We propose a set of postulates that an extended framework should satisfy and consider two instantiations of the framework: (locally preferred) l-repairs and(More)
We propose shape expression schema (ShEx), a novel schema formalism for describing the topology of an RDF graph that uses regular bag expressions (RBEs) to define constraints on the admissible neighborhood for the nodes of a given type. We provide two alternative semantics, multi-and single-type, depending on whether or not a node may have more than one(More)
Integrity constraints express important properties of data, but the task of preserving data consistency is becoming increasingly problematic with new database applications. For example, in the case of integration of several data sources, even if the sources are separately consistent, the integrated data can violate the integrity constraints. The traditional(More)
We investigate the problem of learning XML queries, <i>path</i> queries and <i>twig</i> queries, from examples given by the user. A learning algorithm takes on the input a set of XML documents with nodes annotated by the user and returns a query that selects the nodes in a manner consistent with the annotation. We study two learning settings that differ(More)
We study the equivalence problem of deterministic nested word to word transducers and show it to be surprisingly robust. Modulo polynomial time reductions, it can be identified with 4 equivalence problems for diverse classes of deterministic non-copying order-preserving transducers. In particular, we present polynomial time back and fourth reductions to the(More)
One of the goals of cleaning an inconsistent database is to remove conflicts between tuples. Typically, the user specifies how the conflicts should be resolved. Sometimes this specification is incomplete, and the cleaned database may still be inconsistent. At the same time, data cleaning is a rather drastic approach to conflict resolution: It removes tuples(More)