We introduce a novel logic-based system for reasoning over data streams, which relies on a framework enabling a tight, fine-tuned interaction between Apache Flink and the $${{\mathcal I}^2}$$ -DLV system. The architecture allows to take... more
We introduce a novel logic-based system for reasoning over data streams, which relies on a framework enabling a tight, fine-tuned interaction between Apache Flink and the $${{\mathcal I}^2}$$ -DLV system. The architecture allows to take advantage from both the powerful distributed stream processing capabilities of Flink and the incremental reasoning capabilities of $${{\mathcal I}^2}$$ -DLV, based on overgrounding techniques. Besides the system architecture, we illustrate the supported input language and its modeling capabilities, and discuss the results of an experimental activity aimed at assessing the viability of the approach.
Research Interests:
Decision support systems play an important role in medical fields as they can augment clinicians to deal more efficiently and effectively with complex decision-making processes. In the diagnosis of headache disorders, however, existing... more
Decision support systems play an important role in medical fields as they can augment clinicians to deal more efficiently and effectively with complex decision-making processes. In the diagnosis of headache disorders, however, existing approaches and tools are still not optimal. On the one hand, to support the diagnosis of this complex and vast spectrum of disorders, the International Headache Society released in 1988 the International Classification of Headache Disorders (ICHD), now in its 3rd edition: a 200 pages document classifying more than 300 different kinds of headaches, where each is identified via a collection of specific nontrivial diagnostic criteria. On the other hand, the high number of headache disorders and their complex criteria make the medical history process inaccurate and not exhaustive both for clinicians and existing automatic tools. To fill this gap, we present head-asp, a novel decision support system for the diagnosis of headache disorders. Through a REST W...
Research Interests:
The W3C Web Ontology Language (OWL) is a powerful knowledge representation formalism at the basis of many semantic-centric applications. Since its unrestricted usage makes reasoning undecidable already in case of very simple tasks,... more
The W3C Web Ontology Language (OWL) is a powerful knowledge representation formalism at the basis of many semantic-centric applications. Since its unrestricted usage makes reasoning undecidable already in case of very simple tasks, expressive yet decidable fragments have been identified. Among them, we focus on OWL 2 RL, which offers a rich variety of semantic constructors, apart from supporting all RDFS datatypes. Although popular Web resources - such as DBpedia - fall in OWL 2 RL, only a few systems have been designed and implemented for this fragment. None of them, however, fully satisfy all the following desiderata: (i) being freely available and regularly maintained; (ii) supporting query answering and SPARQL queries; (iii) properly applying the sameAs property without adopting the unique name assumption; (iv) dealing with concrete datatypes. To fill the gap, we present DaRLing, a freely available Datalog rewriter for OWL 2 RL ontological reasoning under SPARQL queries. In part...
Research Interests:
With the more and more growing demand for semantic Web services over large databases, an efficient evaluation of Datalog queries is arousing a renewed interest among researchers and industry experts. In this scenario, to reduce memory... more
With the more and more growing demand for semantic Web services over large databases, an efficient evaluation of Datalog queries is arousing a renewed interest among researchers and industry experts. In this scenario, to reduce memory consumption and possibly optimize execution times, the paper proposes novel techniques to determine an optimal indexing schema for the underlying database together with suitable body-orderings for the Datalog rules. The new approach is compared with the standard execution plans implemented in DLV over widely used ontological benchmarks. The results confirm that the memory usage can be significantly reduced without paying any cost in efficiency.
Research Interests:
Research Interests:
Research Interests:
Ontology-based query answering asks whether a Boolean conjunctive query is satisfied by all models of a logical theory consisting of a relational database paired with an ontology. The introduction of existential rules (i.e., Datalog rules... more
Ontology-based query answering asks whether a Boolean conjunctive query is satisfied by all models of a logical theory consisting of a relational database paired with an ontology. The introduction of existential rules (i.e., Datalog rules extended with existential quantifiers in rule heads) as a means to specify the ontology gave birth to Datalog+/-, a framework that has received increasing attention in the last decade, with focus also on decidability and finite controllability to support effective reasoning. Five basic decidable fragments have been singled out: linear, weakly acyclic, guarded, sticky, and shy. Moreover, for all these fragments, except shy, the important property of finite controllability has been proved, ensuring that a query is satisfied by all models of the theory iff it is satisfied by all its finite models. In this paper, we complete the picture by demonstrating that finite controllability of ontology-based query answering holds also for shy ontologies, and it ...
Research Interests:
Consistent query answering over a database that violates primary key constraints is a classical hard problem in database research that has been traditionally dealt with logic programming. However, the applicability of existing logic-based... more
Consistent query answering over a database that violates primary key constraints is a classical hard problem in database research that has been traditionally dealt with logic programming. However, the applicability of existing logic-based solutions is restricted to data sets of moderate size. This paper presents a novel decomposition and pruning strategy that reduces, in polynomial time, the problem of computing the consistent answer to a conjunctive query over a database subject to primary key constraints to a collection of smaller problems of the same sort that can be solved independently. The new strategy is naturally modeled and implemented using Answer Set Programming (ASP). An experiment run on benchmarks from the database world prove the effectiveness and efficiency of our ASP-based approach also on large data sets.
Research Interests:
ABSTRACT Recognizing and extracting meaningful information from Web unstructured documents, taking into account their semantics, is an important problem of information and knowledge management. This paper describes H i\imath LεX, a system... more
ABSTRACT Recognizing and extracting meaningful information from Web unstructured documents, taking into account their semantics, is an important problem of information and knowledge management. This paper describes H i\imath LεX, a system implementing a novel logic-based approach to information extraction from unstructured documents. The approach adopted in the H i\imath LεX system is founded on a new two-dimensional representation of documents, and heavily exploits DLP + - an extension of disjunctive logic programming for ontology representation and reasoning, which has been recently implemented on top of the DLV reasoning environment. Unlike previous systems, which are mainly syntactic, H i\imath LεX combines both semantic and syntactic knowledge for a powerful information extraction. Ontologies, representing the semantics of information to be extracted, are encoded in DLP + , while the extraction patterns are expressed using regular expressions and an ad hoc two-dimensional grammar. The execution of DLP + reasoning modules, encoding the grammar expressions, yields the actual extraction of information from the input document. H i\imath LεX allows the semantic information extraction from both HTML pages and flat text documents by using synthetic and very expressive extraction patterns.
Abstract iTravel is an e-tourism system conceived for helping both employees and customers of a travel agency in finding the best possible travel solution in a short time. The core of iTravel is an ontology which models the domain of the... more
Abstract iTravel is an e-tourism system conceived for helping both employees and customers of a travel agency in finding the best possible travel solution in a short time. The core of iTravel is an ontology which models the domain of the touristic offers. The key ...
Research Interests:
Answer Set Programming is a well-established paradigm of declarative programming in close relationship with other declarative formalisms such as SAT Modulo Theories, Constraint Handling Rules, FO (.), PDDL and many others. Since its first... more
Answer Set Programming is a well-established paradigm of declarative programming in close relationship with other declarative formalisms such as SAT Modulo Theories, Constraint Handling Rules, FO (.), PDDL and many others. Since its first informal editions, ASP systems are compared in the nowadays customary ASP Competition. The Third ASP Competition, as the sequel to the ASP Competitions Series held at the University of Potsdam in Germany (2006-2007) and at the University of Leuven in Belgium in 2009, took place at ...
Research Interests: Communication Engineering, Computer Networks, Teletraffics & Queueing Theory, Close relationships, Answer Set Programming, and 6 moreDeclarative Programming, Network Performance, Constraint Handling, Research Quality of Servicing for Stream Traffic in Transport Telecommunication Networks, Real-world Application, and Tele-traffic Engineering
ABSTRACT Datalog∃ is the extension of Datalog allowing existentially quantified variables in rule heads. This language is highly expressive and enables easy and powerful knowledge-modelling, but the presence of existentially quantified... more
ABSTRACT Datalog∃ is the extension of Datalog allowing existentially quantified variables in rule heads. This language is highly expressive and enables easy and powerful knowledge-modelling, but the presence of existentially quantified variables makes reasoning over Datalog∃ undecidable in the general case. Restricted classes of Datalog∃, such as shy, have been proposed in the literature with the aim of enabling powerful, yet decidable query answering on top of Datalog∃ programs. However, in order to make such languages attractive it is necessary to guarantee good performance for query answering tasks. This paper works in this direction: improving the performance of query answering on Datalog∃. To this end, we design a rewriting method extending the well-known Magic-Sets technique to any Datalog∃ program. We demonstrate that our rewriting method preserves query equivalence on Datalog∃, and can be safely applied to shy programs. We therefore incorporate the Magic-Sets method in DLV∃, a system supporting shy. Finally, we carry out an experiment assessing the positive impact of Magic-Sets on DLV∃, and the effectiveness of the enhanced DLV∃ system compared to a number of state-of-the-art systems for ontology-based query answering.
Answer Set Programming (ASP) is a declarative language for knowledge representation and reasoning. After its proposal, in a seminal paper by Michael Gelfond and Vladimir Lifschitz dated in 1988, ASP has been the subject of a broad... more
Answer Set Programming (ASP) is a declarative language for knowledge representation and reasoning. After its proposal, in a seminal paper by Michael Gelfond and Vladimir Lifschitz dated in 1988, ASP has been the subject of a broad theoretical research-work, ranging from linguistic extensions and semantic properties to evaluation algorithm and optimization techniques. Later on, the availability of a number of efficient systems made ASP a powerful tool for the fast development of knowledge-based applications. In this paper, we report on ...
... In this case a specific workflow schema and the related instance are created at each ... applied to obtain a real world application in the field of health care risk management. ... diagnosis data (diagnosis time, kind of tumor, body... more
... In this case a specific workflow schema and the related instance are created at each ... applied to obtain a real world application in the field of health care risk management. ... diagnosis data (diagnosis time, kind of tumor, body part affected by the cancer, cancer progression level ...
Research Interests: Data Mining, Patient Safety, Health Care, Pattern Recognition, Risk Management, and 12 moreKnowledge Representation, Ontologies, Process management, Patient Monitoring, Heart, Knowledge Acquisition, Semantic Information, Domain Knowledge, Knowledge base, Knowledge Modelling, Medical Error, and Cost Control
The seaport of Gioia Tauro is the largest transshipment terminal of the Mediterranean coast. A crucial management task for the companies operating in the seaport is team-building: the problem of properly allocating the available personnel... more
The seaport of Gioia Tauro is the largest transshipment terminal of the Mediterranean coast. A crucial management task for the companies operating in the seaport is team-building: the problem of properly allocating the available personnel for serving the incoming ships. Teams have to be carefully arranged in order to meet several constraints, such as allocation of employees with appropriate skills, fair distribution of the working load, and turnover of the heavy/dangerous roles. This makes team-building a hard and expensive task requiring several hours of manual preparation per day.In this paper we present a system based on Answer Set Programming for the automatic generation of the teams of employees in the seaport of Gioia Tauro. The system is currently exploited in the Gioia Tauro seaport by ICO BLG, a company specialized in automobile logistics.
Research Interests:
Existential rules are Datalog rules extended with existential quantifiers in rule-heads. Three fundamental restriction paradigms that have been studied for ensuring decidability of query answering under existential rules are... more
Existential rules are Datalog rules extended with existential quantifiers in rule-heads. Three fundamental restriction paradigms that have been studied for ensuring decidability of query answering under existential rules are weak-acyclicity, guardedness and stickiness. Towards the identification of even more expressive decidable languages, several attempts have been conducted to consolidate weak-acyclicity with the other two paradigms. However, it is not clear how guardedness and stickiness can be merged; this is the subject of this paper. A powerful and flexible condition, called tameness, is proposed, which allows us to consolidate in an elegant and uniform way guardedness with stickiness.
Research Interests:
Datalogis one of the best-known rule-based languages, and extensions of it are used in a wide context of applications. An importantDatalogextension is DisjunctiveDatalog, which significantly increases the expressivity of the basic... more
Datalogis one of the best-known rule-based languages, and extensions of it are used in a wide context of applications. An importantDatalogextension is DisjunctiveDatalog, which significantly increases the expressivity of the basic language. DisjunctiveDatalogis useful in a wide range of applications, ranging from Databases (e.g., Data Integration) to Artificial Intelligence (e.g., diagnosis and planning under incomplete knowledge). However, in recent years an important shortcoming ofDatalog-based languages became evident, e.g. in the context of data-integration (consistent query-answering, ontology-based data access) and Semantic Web applications: The language does not permit any generation of and reasoning with unnamed individuals in an obvious way. In general, it is weak in supporting many cases of existential quantification. To overcome this problem,Datalog∃has recently been proposed, which extends traditionalDatalogby existential quantification in rule heads. In this work, we pr...
Research Interests:
A data integration system provides transparent access to different data sources by suitably combining their data, and providing the user with a unified view of them, calledglobal schema. However, source data are generally not under the... more
A data integration system provides transparent access to different data sources by suitably combining their data, and providing the user with a unified view of them, calledglobal schema. However, source data are generally not under the control of the data integration process; thus, integrated data may violate global integrity constraints even in the presence of locally consistent data sources. In this scenario, it may be anyway interesting to retrieve as much consistent information as possible. The process of answering user queries under global constraint violations is calledconsistent query answering(CQA). Several notions of CQA have been proposed, e.g., depending on whether integrated information is assumed to besound,complete,exact, or a variant of them. This paper provides a contribution in this setting: it uniforms solutions coming from different perspectives under a common Answer-Set Programming (ASP)-based core, and provides query-driven optimizations designed for isolating a...
Research Interests:
Research Interests:
... 13. Valter Crescenzi , Giansalvatore Mecca , Paolo Merialdo, RoadRunner: Towards Automatic Data Extraction from Large Web Sites, Proceedings ... 21. Oren Etzioni , Michael Cafarella , Doug Downey , Stanley Kok , Ana-Maria Popescu ,... more
... 13. Valter Crescenzi , Giansalvatore Mecca , Paolo Merialdo, RoadRunner: Towards Automatic Data Extraction from Large Web Sites, Proceedings ... 21. Oren Etzioni , Michael Cafarella , Doug Downey , Stanley Kok , Ana-Maria Popescu , Tal Shaked , Stephen Soderland , Daniel ...
Research Interests:
Research Interests:
... m(Xc) :− man(Xc, ). e(Xc,Xn) :− employee(Xc,Xn, ). m(Xc) :− employee(Xc, , 'manager ). Assume that, emp stores tuples ('e1','john'), ('e2','mary'), ('e3','willy'), man... more
... m(Xc) :− man(Xc, ). e(Xc,Xn) :− employee(Xc,Xn, ). m(Xc) :− employee(Xc, , 'manager ). Assume that, emp stores tuples ('e1','john'), ('e2','mary'), ('e3','willy'), man stores ('e1','john'), and employee stores ('e1','ann','manager'), ('e2','mary','manager'), ('e3','rose','emp'). ...
Regular grammars with attributes overcome some limitations of classical regular grammars, sensibly enhancing their expressiveness. However, the addition of attributes increases the complexity of this formalism leading to intractability in... more
Regular grammars with attributes overcome some limitations of classical regular grammars, sensibly enhancing their expressiveness. However, the addition of attributes increases the complexity of this formalism leading to intractability in the general case. In this paper, we consider regular grammars with attributes ranging over integers, providing an in-depth complexity analysis. We identify relevant fragments of tractable attribute grammars, where complexity