Enrico Franconi

Libera Università di Bozen-Bolzano, Bozen, Trentino-Alto Adige, Italy

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Publications (193)28.88 Total impact

  • Ingo Feinerer · Enrico Franconi · Paolo Guagliardo
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    ABSTRACT: A set of views defined by selection queries splits a database relation into sub-relations, each containing a subset of the original rows. This decomposition into horizontal fragments is lossless when the initial relation can be reconstructed from the fragments by union. In this paper, we consider horizontal decomposition in a setting where some of the attributes in the database schema are interpreted over a specific domain, on which a set of special predicates and functions is defined. We study losslessness in the presence of integrity constraints on the database schema. We consider the class of conditional domain constraints (CDCs), which restrict the values that the interpreted attributes may take whenever a certain condition holds on the non-interpreted ones, and investigate lossless horizontal decomposition under CDCs in isolation, as well as in combination with functional and unary inclusion dependencies.
    No preview · Article · Jun 2015 · IEEE Transactions on Knowledge and Data Engineering
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    Preview · Article · Oct 2014
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    ABSTRACT: In this paper we define the first-order fragment of the Object Constraint Language (OCL), the declarative language for describing rules that apply to conceptual schemas in the Unified Modelling Language (UML). This fragment covers the whole of OCL without arithmetic operators, aggregation functions, iterators, and recursion. We give the set theoretical formal syntax and semantics in an elegant, concise, and clear way. This fragment has the same expressivity as domain-independent first-order logic (aka relational algebra), in the sense that any relational algebra expression can be reformulated as a logically equivalent OCL expression, and vice-versa.
    No preview · Article · Sep 2014 · Lecture Notes in Computer Science
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    Laura Perez-Beltrachini · Claire Gardent · Enrico Franconi
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    ABSTRACT: We present a natural language generation system which supports the incremental specification of ontology-based queries in natural language. Our contribution is two fold. First, we introduce a chart based surface realisation algorithm which supports the kind of incremental processing required by ontology-based querying. Crucially, this algorithm avoids confusing the end user by preserving a consistent ordering of the query elements throughout the incremental query formulation process. Second, we show that grammar based surface realisation better supports the generation of fluent, natural sounding queries than previous template-based approaches.
    Preview · Article · Apr 2014
  • N. Ngo · E. Franconi
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    ABSTRACT: Data exchange is the problem of transforming data structured according to a source schema into data structured according to a target schema, via a mapping specified by rules in the form of source-to-target tuple generating dependencies. In this context, given a source instance and a mapping, there might be more than one valid target instance that satisfies the mapping. This issue contradicts the main goal of exchanging data, namely to have a materialized target instance that can be used to answer queries over the target schema without reference to the original source instance. In this paper we introduce and solve the novel problem of definability abduction, which aims at finding extensions to the initial schema mappings to guarantee the uniqueness of the materialized target instance. We consider several semantic criteria to select reasonable extensions and provide provably sound and complete algorithms to generate these additions. We also do a complexity analysis in different data exchange settings, also with source and target dependencies. Copyright © (2014) by Universita Reggio Calabria & Centro di Competenza (ICT-SUD) All rights reserved.
    No preview · Article · Jan 2014
  • I. Feinerer · E. Franconi · P. Guagliardo

    No preview · Article · Jan 2014
  • Enrico Franconi · Volha Kerhet · Nhung Ngo
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    ABSTRACT: We study a general framework for query rewriting in the presence of an arbitrary first-order logic ontology over a database signature. The framework supports deciding the existence of a safe-range first-order equivalent reformulation of a query in terms of the database signature, and if so, it provides an effective approach to construct the reformulation based on interpolation using standard theorem proving techniques (e.g., tableau). Since the reformulation is a safe-range formula, it is effectively executable as an SQL query. At the end, we present a non-trivial application of the framework with ontologies in the very expressive ALCHOIQ description logic, by providing effective means to compute safe-range first-order exact reformulations of queries.
    No preview · Article · Oct 2013 · Journal of Artificial Intelligence Research
  • Nhung Ngo · Enrico Franconi
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    ABSTRACT: A schema mapping is a high-level specification in which the relationship between two database schemas is described. In data exchange, schema mappings are one-way mappings that describe which data can be brought from source data to target data. Therefore, given a source instance and a mapping, there might be more than one valid target instance. This fact causes many problems in query answering over target data for non-conjunctive queries. To make query answering feasible for all queries, we focus on a methodology for extending the original schema mapping to guarantee the uniqueness of target instance corresponding to a source instance. To this end, we introduce a theoretical framework where the problem is transformed to an abduction problem, namely, definability abduction. We apply the framework to relational data exchange setting and solve the problem by pointing out minimal solutions according to a specific semantic minimality criterion.
    No preview · Article · Aug 2013 · Proceedings of the VLDB Endowment
  • Ingo Feinerer · Enrico Franconi · Paolo Guagliardo
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    ABSTRACT: Horizontal decomposition is the process of splitting a relation into sub-relations, called fragments, each containing a subset of the rows of the original relation. In this paper, we consider horizontal decomposition in a setting where some of the attributes in the database schema are interpreted over a specific domain, on which a set of special predicates and functions is defined. We study the losslessness of horizontal decomposition, that is, whether the original relation can be reconstructed from the fragments by union, in the presence of integrity constraints on the database schema. We introduce the new class of conditional domain constraints (CDCs), restricting the values the interpreted attributes may take whenever a certain condition holds on the non-interpreted ones, and investigate lossless horizontal decomposition under CDCs in isolation, as well as in combination with functional and unary inclusion dependencies.
    No preview · Conference Paper · Jul 2013
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    ABSTRACT: The normative version of RDF Schema (RDFS) gives non-standard (intensional) interpretations to some standard notions such as classes and properties, thus departing from standard set-based semantics. In this paper we develop a standard set-based (extensional) semantics for the RDFS vocabulary while preserving the simplicity and computa-tional complexity of deduction of the intensional version. This result can positively impact current implementations, as reasoning in RDFS can be implemented following common set-based intuitions and be compatible with OWL extensions.
    Full-text · Conference Paper · Jan 2013
  • E. Franconi · P. Guagliardo

    No preview · Article · Jan 2013
  • E. Franconi · C. Gutierrez · A. Mosca · G. Pirrò · R. Rosati
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    ABSTRACT: The normative version of RDFS gives non-standard (intensional) interpretations to some standard notions such as classes and properties. In this paper we develop the extensional semantics for the RDFS vocabulary, which surprisingly preserves the simplicity and computational complexity of deduction of the intensional case. This result will impact current implementations in a positive sense, as reasoning in RDFS will follow common set-based intuitions and be compatible with OWL extensions; moreover, the rule system that we present is easily embeddable in existing libraries such as Jena.
    No preview · Article · Jan 2013
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    Enrico Franconi · Paolo Guagliardo
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    ABSTRACT: In this paper, we revisit the view update problem in a relational setting and propose a framework based on the notion of determinacy under constraints. Within such a framework, we characterise when a view mapping is invertible, establishing that this is the case precisely when each database symbol has an exact rewriting in terms of the view symbols under the given constraints, and we provide a general effective criterion to understand whether the changes introduced by a view update can be propagated to the underlying database relations in a unique and unambiguous way. Afterwards, we show how determinacy under constraints can be checked, and rewritings effectively found, in three different relevant scenarios in the absence of view constraints. First, we settle the long-standing open issue of how to solve the view update problem in a multi-relational database with views that are projections of joins of relations, and we do so in a more general setting where views are defined by arbitrary conjunctive queries and database constraints are stratified embedded dependencies. Next, we study a setting based on horizontal decompositions of a single database relation, where views are defined by selections on possibly interpreted attributes (e.g., arithmetic comparisons) in the presence of domain constraints over the database schema. Lastly, we look into another multi-relational database setting, where views are defined in an expressive "Type" Relational Algebra based on the n-ary Description Logic DLR and database constraints are inclusions of expressions in that algebra.
    Preview · Article · Nov 2012
  • Peter F. Patel-Schneider · Enrico Franconi
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    ABSTRACT: Ontology and other logical languages are built around the idea that axioms enable the inference of new facts about the available data. In some circumstances, however, the data is meant to be complete in certain ways, and deducing new facts may be undesirable. Previous approaches to this issue have relied on syntactically specifying certain axioms as constraints or adding in new constructs for constraints, and providing a different or extended meaning for constraints that reduces or eliminates their ability to infer new facts without requiring the data to be complete. We propose to instead directly state that the extension of certain concepts and roles are complete by making them DBox predicates, which eliminates the distinction between regular axioms and constraints for these concepts and roles. This proposal eliminates the need for special semantics and avoids problems of previous proposals.
    No preview · Conference Paper · Nov 2012
  • Enrico Franconi · Nhung Ngo · Evgeny Sherkhonov
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    ABSTRACT: Data exchange is the problem of transforming data structured according to a source schema into data structured according to a target schema, via a mapping specified by means of rules in the form of source-to-targettuplegeneratingdependencies --- rules whose body is a conjunction of atoms over the source schema and the head is a conjunction of atoms over the target schema, with possibly existential variables in the head. With this formalization, given a fixed source database, there might be more than one target databases satisfying a given mapping. That is, the target database is actually an incompletedatabase represented by a set of possible databases. Therefore, the problem of query answering the target data is inherently complex for general (non-positive) relational or aggregate queries.
    No preview · Conference Paper · Sep 2012
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    Enrico Franconi · Paolo Guagliardo
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    ABSTRACT: In this article, we revisit the view update framework by Ban-cilhon and Spyratos in a setting with constraints expressed in first-order logic. We explicitly consider constraints on both the database and the view schemas, along with inter-schema constraints that implicitly define the view mappings. Using the notion of logical definability we give a con-structive characterisation of views, their inverses and complements, and provide an effective method for checking whether an arbitrary first-order expressible view update can be (uniquely) translated under the constant complement principle.
    Preview · Article · May 2012
  • E. Franconi · A. Mosca · D. Solomakhin
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    ABSTRACT: The Object Role Modelling (ORM2) is a conceptual modelling approach combining both textual specifications and graphical language, similar to UML and ER, and adopted by Visual Studio, the integrated development environment designed by Microsoft. This paper introduces a new linear syntax and corresponding complete set-theoretic semantics for a generalization of ORM2 language. A core fragment of ORM2 is defined, for which a provably correct encoding into ALCQI description logic is presented. Based on these results, an extensive and systematic critique of alternative approaches to the formalization of ORM2 in (description) logics published so far is provided. A first prototype has been implemented, which offers a back-end for the automated support of consistency and entailment checks for ORM2 conceptual schemas along with its translation into ALCQI knowledge bases.
    No preview · Article · Jan 2012
  • E. Franconi · S. Tessaris
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    ABSTRACT: The logic of nulls in databases has been subject of investigation since their introduction in Codd's Relational Model, which is the foundation of the SQL standard. In the logic based approaches to modelling relational databases proposed so far, nulls are considered as representing unknown values. Such existential semantics fails to capture the behaviour of the SQL standard. We show that, according to Codd's Relational Model, a SQL null value represents a non-existing value; as a consequence no indeterminacy is introduced by SQL null values.We show that the domain independent fragment of the extension of first-order logic accounting for predicates with missing arguments is equivalent to Codd's relational algebra with SQL nulls. Moreover, we illustrate a faithful encoding of the logic into standard first-order logic. At the end, we show how to capture in this framework the UNIQUE, PRIMARY KEY, and FOREIGN KEY constraints as defined in the SQL:1999 standard.
    No preview · Article · Jan 2012
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    Paolo Guagliardo · Enrico Franconi
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    ABSTRACT: We revisit the view update problem and the abstract functional framework by Bancilhon and Spyratos in a setting where views and updates are exactly given by functions that are expressible in first-order logic. We give a characterisation of views and their inverses based on the notion of definability, and we introduce a general method for checking whether a view update can be uniquely translated as an update of the underlying database under the constant complement principle. We study the setting consisting of a single database relation and two views defined by projections and compare our general criterion for translatability with the known results for the case in which the constraints on the database are given by functional dependencies. We extend the setting to any number of projective views, full dependencies (that is, egd's and full tgd's) as database constraints, and classes of updates rather than single updates.
    Preview · Article · Jan 2012
  • E. Franconi · V. Kerhet · N. Ngo
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    ABSTRACT: We formalise the problem of query reformulation over a description logic ontology and a DBox in a general framework. This framework supports deciding the existence of a safe-range first-order equivalent reformulation of a concept query in terms of the signature of a DBox. A constructive method to compute the reformulation is provided.We are particularly interested in safe-range reformulations since they can be transformed to relational queries and executed using SQL. We also discuss the completeness of the proposed framework with respect to finite and unrestricted models. As a case study we consider ontologies and queries expressed in SHOQ.
    No preview · Article · Jan 2012

Publication Stats

3k Citations
28.88 Total Impact Points

Institutions

  • 2002-2015
    • Libera Università di Bozen-Bolzano
      • Faculty of Computer Science
      Bozen, Trentino-Alto Adige, Italy
  • 1999-2004
    • The University of Manchester
      • School of Computer Science
      Manchester, England, United Kingdom
  • 2003
    • Sapienza University of Rome
      Roma, Latium, Italy
  • 1992-2002
    • Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori
      Meldola, Emilia-Romagna, Italy