Giorgio Orsi

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Ontological queries are evaluated against an enterprise ontology rather than directly on a database. The evaluation and optimization of such queries is an intriguing new problem for database research. In this paper we discuss two important aspects of this problem: query rewriting and query optimization. Query rewriting consists of the compilation of an(More)
Search engines are the sinews of the web. These sinews have become strained, however: Where the web's function once was a mix of library and yellow pages, it has become the central marketplace for information of almost any kind. We search more and more for objects with specific characteristics, a car with a certain mileage, an affordable apartment close to(More)
Ontological queries are evaluated against a knowledge base consisting of an extensional database and an ontology (i.e., a set of logical assertions and constraints that derive new intensional knowledge from the extensional database), rather than directly on the extensional database. The evaluation and optimization of such queries is an intriguing new(More)
Forms are our gates to the web. They enable us to access the deep content of web sites. Automatic form understanding unlocks this content for applications ranging from crawlers to meta-search engines and is essential for improving usability and accessibility of the web. Form understanding has received surprisingly little attention other than as component in(More)
Ontological queries are evaluated against an ontology rather than directly on a database. The evaluation and optimization of such queries is an intriguing new problem for database research. In this paper we discuss two important aspects of this problem: query rewriting and query optimization. Query rewriting consists of the compilation of an ontological(More)
Ontological queries are evaluated against a database combined with ontological constraints. Answering such queries is a challenging new problem for database research. For many ontological modelling languages, query answering can be solved via query rewriting: given a conjunctive query and an ontology, the query can be transformed into a first-order query,(More)
We present NYAYA, a flexible system for the management of large-scale semantic data which couples a general-purpose storage mechanism with efficient ontological query answering. NYAYA rapidly imports semantic data expressed in different formalisms into semantic data kiosks. Each kiosk exposes the native ontological constraints in a uniform fashion using(More)
This paper summarizes the results of the X-SOM tool in the OAEI 2007 campaign. X-SOM is an extensible ontology mapper that combines various matching algorithms by means of a feed-forward neural network. X-SOM exploits logical reasoning and local heuristics to improve the quality of mappings while guaranteeing their consistency. 1 Presentation of the system(More)
Relational databases have been designed to store high volumes of data and to provide an efficient query interface. Ontologies are geared towards capturing domain knowledge, annotations, and to offer high-level, machine-processable views of data and metadata. The complementary strengths and weaknesses of these data models motivate the research effort we(More)