Enrico Franconi

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

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Publications (173)16.5 Total impact

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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.
    Lecture Notes in Computer Science 01/2014; 8761:657-664. · 0.51 Impact Factor
  • 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.
    Journal of Artificial Intelligence Research 10/2013; 48(1):885-922. · 1.06 Impact Factor
  • 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.
    Proceedings of the VLDB Endowment. 08/2013; 6(12):1440-1443.
  • 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.
    Proceedings of the 29th British National conference on Big Data; 07/2013
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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.
    International Semantic Web Conference; 01/2013
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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.
    11/2012;
  • 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.
    Proceedings of the 11th international conference on The Semantic Web - Volume Part I; 11/2012
  • 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.
    Proceedings of the 6th international conference on Web Reasoning and Rule Systems; 09/2012
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    Balder ten Cate, Enrico Franconi, Inanç Seylan
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    ABSTRACT: The Beth definability property, a well-known property from classical logic, is investigated in the context of description logics (DLs): if a general LTBox implicitly defines an L-concept in terms of a given signature, where L is a DL, then does there always exist over this signature an explicit definition in L for the concept? This property has been studied before and used to optimize reasoning in DLs. In this paper a complete classification of Beth definability is provided for extensions of the basic DL ALC with transitive roles, inverse roles, role hierarchies, and/or functionality restrictions, both on arbitrary and on finite structures. Moreover, we present a tableau-based algorithm which computes explicit definitions of at most double exponential size. This algorithm is optimal because it is also shown that the smallest explicit definition of an implicitly defined concept may be double exponentially long in the size of the input TBox. Finally, if explicit definitions are allowed to be expressed in first-order logic then we show how to compute them in EXPTIME.
    IJCAI 2011, Proceedings of the 22nd International Joint Conference on Artificial Intelligence, Barcelona, Catalonia, Spain, July 16-22, 2011; 01/2011
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    Proceedings of the 24th International Workshop on Description Logics (DL 2011), Barcelona, Spain, July 13-16, 2011; 01/2011
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    ABSTRACT: Data in description logic knowledge bases is stored in the form of an ABox. ABoxes are often confusing for developers coming from relational databases because an ABox, in contrast to a database instance, provides an incomplete specification. A recently introduced assertional component of a description logic knowledge base is a DBox, which behaves more like a database instance. In this paper, we study the data complexity of query answering in the description logic DL-LiteF extended with DBoxes. DL-LiteF is a description logic tailored for data intensive applications and the data complexity of query answering in DL-LiteF with ABoxes is tractable (in AC0). Our main result is that this problem becomes coNP-complete with DBoxes. In some expressive description logics, query answering with DBoxes also leads to a higher (combined) complexity than query answering with ABoxes. As a proof of concept, we relate query answering in ALCFIO, i.e., ALC with Functional and Inverse roles, and nOminals to the same problem in ALCFI with DBoxes. The exact complexity of the former is an open problem in the description logic literature. Here we show that query answering in ALCFIO and ALCFI with DBoxes are mutually reducible to each other in polynomial time.All the proofs in this paper are available in the appendix for the reviewersʼ convenience.
    Electr. Notes Theor. Comput. Sci. 01/2011; 278:71-84.
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    Enrico Franconi, David Toman
    IJCAI 2011, Proceedings of the 22nd International Joint Conference on Artificial Intelligence, Barcelona, Catalonia, Spain, July 16-22, 2011; 01/2011
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    Proceedings of the 24th International Workshop on Description Logics (DL 2011), Barcelona, Spain, July 13-16, 2011; 01/2011
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    ABSTRACT: Automated support to enterprise modeling has increasingly become a subject of interest for organizations seeking solutions for storage, distribution and analysis of knowledge about business processes. This interest has recently resulted in approving the standard for specifying Semantics of Business Vocabulary and Business Rules SBVR. Despite the existence of formally grounded notations, up to now SBVR still lacks a sound and consistent logical formalization which would allow developing automated solutions able to check the consistency of a set of business rules. This work reports on the attempt to provide logical foundations for SBVR by the means of defining a specific first-order deontic-alethic logic FODAL. The connections of FODAL with the modal logic QK and the description logic ALCQI have been investigated and, on top of the obtained theoretical results, a special tool providing automated support for consistency checks of a set of ALCQI-expressible deontic and alethic business rules has been implemented.
    Proceedings of the 26th Italian Conference on Computational Logic (CILC2011), Pescara, Italy, 31 August 31-2 September, 2011; 01/2011
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    E Franconi, T Meyer, I Varzinczak
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    ABSTRACT: 13th International Workshop on Non-Monotonic Reasoning (NMR). 14-16 May 2010, Toronto, Canada In this paper the authors investigate the problem of maintaining and reasoning with different versions of a knowledge base. The authors are interested in the scenario where a knowledge base (expressed in some logical formalism) might evolve over time and, as a consequence, different versions thereof have to be maintained simultaneously in a parsimonious way. Moreover, users of the knowledge base should be able to access, not only any specific version, but also the differences between two given versions of the knowledge base. The authors address this problem by proposing a general semantic framework for the maintenance of different versions of a knowledge base. It turns out that the notion of semantic difference between knowledge bases plays a central role in the framework. The authors show that an appropriate characterization produces a unique definition of semantic difference which is applicable to a large class of logic-based knowledge representation languages. The authors then proceed to restrict our attention to finitely generated propositional logics, and show that our semantic framework can be represented syntactically in a particular kind of normal form, referred to as ordered complete conjunctive normal form or oc-CNF. This is followed by a generalization in which the authors show that similar results can be obtained for any syntactic representation (in a finitely generated propositional logic) of the semantic framework. Of particular interest are representations of appropriately chosen normal forms. The authors expect that our constructions for the propositional case can be extended to more expressive languages, such as description logics (DLs). In that respect, our results add to the investigation of the versioning problem for DL-based ontologies
    01/2010;
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    Enrico Franconi, Paolo Guagliardo, Marco Trevisan
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    ABSTRACT: In this paper we present a formal framework and an experi-mental software supporting the user in the task of formulat-ing a precise query – which best captures their information needs – even in the case of complete ignorance of the vocab-ulary of the underlying information system holding the data. Our intelligent interface is driven by means of appropriate automated reasoning techniques over an ontology describ-ing the domain of the data in the information system. We will define what a query is and how it is internally repre-sented, which operations are available to the user in order to modify the query and how contextual feedback is provided about it presenting only relevant pieces of information. We will then describe the elements that constitute the query in-terface available to the user, providing visual access to the underlying reasoning services and operations for query ma-nipulation. Lastly, we will define a suitable representation in "linear form", starting from which the query can be more easily expressed in natural language.
    01/2010;
  • Proceedings of 1st Workshop on Law Compliancy Issues in Organisational Systems and Strategies; 01/2010
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    Proceedings of the Eighteenth Italian Symposium on Advanced Database Systems, SEBD 2010, Rimini, Italy, June 20-23, 2010; 01/2010
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    Inanç Seylan, Enrico Franconi, Jos de Bruijn
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    ABSTRACT: In this paper, we revisit the problem of definitorial completeness, i.e., whether a given general TBox T in a description logic (DL) L can be rewritten to an acyclic TBox Tin L. This is an important problem because crucial opti- misations in DL reasoners rely on acyclic parts in TBoxes. It is known that such rewritings are possible for definitorial TBoxes in ALC and in logics ALCX for X ⊆ {S, H, I}. Here we establish optimal bounds on the sizes of the result- ing acyclic TBoxes. In particular, we reduce the known triple exponential upper bound on ALC-TBoxes to single exponential. Additionally, we prove the same upper bound for those extensions with X ⊆ {S, H, I} for which there was no es- tablished result before. This means, together with the already known exponential lower bound for ALC, that our bounds are tight.
    Proceedings of the 23rd International Workshop on Description Logics (DL 2010), Waterloo, Ontario, Canada, May 4-7, 2010; 01/2010
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    ABSTRACT: ICOM (version 3.0) is an advanced conceptual modelling tool, which allows the user to design multiple ex-tended ontologies. Each project can be organised into sev-eral ontologies, with the possibility to include inter-and intra-ontology constraints. Complete logical reasoning is employed by the tool to verify the specification, infer implicit facts, devise stricter constraints, and manifest any inconsis-tency. ICOM is fully integrated with a very powerful descrip-tion logic reasoning server which acts as a background infer-ence engine. The intention behind ICOM is to provide a sim-ple conceptual modelling tool that demonstrates the use of, and stimulates interest in, the novel and powerful knowledge representation based technologies for database and ontology design.
    Applicability. 01/2010;

Publication Stats

2k Citations
16.50 Total Impact Points

Institutions

  • 2002–2013
    • Libera Università di Bozen-Bolzano
      • Faculty of Computer Science
      Bozen, Trentino-Alto Adige, Italy
  • 2011
    • Universität Bremen
      Bremen, Bremen, Germany
  • 2010
    • Universidad Nacional del Sur
      Bahía Blanca, Buenos Aires, Argentina
  • 2005
    • Carleton University
      • School of Computer Science
      Ottawa, Ontario, Canada
  • 1999–2004
    • The University of Manchester
      • School of Computer Science
      Manchester, England, United Kingdom