The MASTRO system for ontology-based data access

Calvanese, Diego; Giacomo, Giuseppe De; Lembo, Domenico; Lenzerini, Maurizio; Poggi, Antonella; Rodríguez-Muro, Mariano; Rosati, Riccardo; Ruzzi, Marco; Savo, Domenico Fabio

doi:10.3233/sw-2011-0029

Cited by 200 publications

(121 citation statements)

References 26 publications

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“…In this example, we present a TBox that models a (very small portion of) the network managed by a telecommunication company, extracted from an ontology we developed within a real-world experimentation [21]. In particular, our KB focuses on the connections between telecommunication devices (cf.…”

Section: Definitionmentioning

confidence: 99%

Inconsistency-Tolerant Query Answering in Ontology-Based Data Access

Lembo¹,

Lenzerini²,

Rosati³

et al. 2015

SSRN Journal

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Ontology-based data access (OBDA) is receiving great attention as a new paradigm for managing information systems through semantic technologies. According to this paradigm, a Description Logic ontology provides an abstract and formal representation of the domain of interest to the information system, and is used as a sophisticated schema for accessing the data and formulating queries over them. In this paper, we address the problem of dealing with inconsistencies in OBDA. Our general goal is both to study DL semantical frameworks that are inconsistency-tolerant, and to devise techniques for answering unions of conjunctive queries under such inconsistency-tolerant semantics. Our work is inspired by the approaches to consistent query answering in databases, which are based on the idea of living with inconsistencies in the database, but trying to obtain only consistent information during query answering, by relying on the notion of database repair. We first adapt the notion of database repair to our context, and show that, according to such a notion, inconsistency-tolerant query answering is intractable, even for very simple DLs. Therefore, we propose a different repair-based semantics, with the goal of reaching a good compromise between the expressive power of the semantics and the computational complexity of inconsistency-tolerant query answering. Indeed, we show that query answering under the new semantics is first-order rewritable in OBDA, even if the ontology is expressed in one of the most expressive members of the DL-Lite family.The results presented in this paper appeared in preliminary form in [46,47,45]. PreliminariesDescription Logics [5] are decidable fragments of first-order logic (FOL) that can be used to represent the knowledge of a domain of interest in a structured and formally well-understood way. They model the domain of interest in terms of objects, i.e., individuals, concepts, that are abstractions for sets of objects, and roles, that denote binary relations between objects. In addition, some DLs distinguish concepts from value-domains, that denote sets of values, and roles from attributes, that denote binary relations between objects and values.We consider an overall alphabet Γ, partitioned in two disjoint alphabets, namely, Γ P , containing symbols for predicates, and Γ C , containing symbols for individual (object and value) constants. We further partition Γ P into four disjoint sets containing symbols denoting atomic concepts, atomic roles, attributes, and value-domains, respectively, and partition Γ C into two disjoint sets, called Γ O and Γ V , which are the set of constants denoting objects, and the set of constants denoting values, respectively. In the rest of the paper, when it is clear from the context, we often implicitly refer to Γ.Complex concept, role, and attribute expressions are constructed by applying suitable operators to atomic concepts and roles, attributes, and value-domains. Different DL languages allow for different operators in the constructs.Given a DL language L, an L ...

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Section: Definitionmentioning

confidence: 99%

Inconsistency-Tolerant Query Answering in Ontology-Based Data Access

Lembo¹,

Lenzerini²,

Rosati³

et al. 2015

SSRN Journal

Self Cite

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“…Yet another type of approaches are [28,160]. DartGrid [160] describes a database integration architecture.…”

Section: Bringing Relational Databases Into the Rdfmentioning

confidence: 99%

RDF 1.1: Knowledge Representation and Data Integration Language for the Web

Tomaszuk

Hyland-Wood

2020

Symmetry

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Resource Description Framework (RDF) can seen as a solution in today's landscape of knowledge representation research. An RDF language has symmetrical features because subjects and objects in triples can be interchangeably used. Moreover, the regularity and symmetry of the RDF language allow knowledge representation that is easily processed by machines, and because its structure is similar to natural languages, it is reasonably readable for people. RDF provides some useful features for generalized knowledge representation. Its distributed nature, due to its identifier grounding in IRIs, naturally scales to the size of the Web. However, its use is often hidden from view and is, therefore, one of the less well-known of the knowledge representation frameworks. Therefore, we summarise RDF v1.0 and v1.1 to broaden its audience within the knowledge representation community. This article reviews current approaches, tools, and applications for mapping from relational databases to RDF and from XML to RDF. We discuss RDF serializations, including formats with support for multiple graphs and we analyze RDF compression proposals. Finally, we present a summarized formal definition of RDF 1.1 that provides additional insights into the modeling of reification, blank nodes, and entailments. arXiv:2001.00432v1 [cs.DB] 2 Jan 2020 organizing information from different information sources. In particular, RDF can be seen as a general proposition language for the Web, which consolidates data from heterogeneous sources. It can provide interoperability between applications that exchange the data.Knowledge representation and data integration in the context of RDF is relevant for several reasons, including: promotes data exchange and interoperability; facilitates the reuse of available systems and tools; enables a fair comparison of Web systems by using benchmarks. In particular, this article shows how the RDF data model can be related to other models.The RDF language enables large portions of existing data to be processed and analyzed. This produces the need to develop the foundations of this language. This article addresses this challenge by developing an abstract model that is suitable to formalize and explain properties about the RDF data. We study the RDF data model, minimal and maximal representations, and show complexity bounds for the main problems. ContributionsWhen we examine the state of the RDF data model, we see evidence of trade-offs that occurred as various constituencies took part in the design process. Many of these trade-offs were never completely summarized in the RDF standards. Our article reviews a final state of RDF, and to identify areas where this data model is poorly understood. Our contributions are:1. to compare the RDF reification approaches, 2. to analyze the RDF 1.1 interpretations, entailments and their complexity, 3. to study the RDF blank nodes and their complexity, 4. to compare the various RDF data integration approaches, 5. to compare the RDF 1.1 serialization formats, including multiple graph syntaxes,...

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“…Ontology-based data access systems, such as Quest, MASTRO and ONDA [5,23,24] focus on mapping relational databases to ontologies in order to perform reasoning during query execution. These systems are restricted to conjunctive queries and do not fully support SPARQL.…”

Section: Related Workmentioning

confidence: 99%

Ultrawrap: SPARQL Execution on Relational Data

Sequeda

Miranker

2013

SSRN Journal

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The Semantic Web's promise to achieve web-wide data integration requires the inclusion of legacy relational data as RDF, which, in turn, requires the execution of SPARQL queries on the legacy relational database. In this paper we explore a hypothesis: existing commercial relational databases already subsume the algorithms and optimizations needed to support effective SPARQL execution on existing relationally stored data. The experiment, embodied in a system called Ultrawrap, comprises encoding a logical representation of the database as a graph using SQL views and a simple syntactic translation of SPARQL queries to SQL queries on those views. Thus, in the course executing a SPARQL query, the SQL optimizer both instantiates a mapping of relational data to RDF and optimizes its execution. Other approaches typically implement aspects of query optimization and execution outside the SQL environment.Ultrawrap is evaluated using two benchmarks across the three major relational database management systems. We identify two important optimizations: detection of unsatisfiable conditions and self-join elimination, such that, when applied, SPARQL queries execute at nearly the same speed as semantically equivalent native SQL queries, providing strong evidence of the validity of the hypothesis.

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The MASTRO system for ontology-based data access

Cited by 200 publications

References 26 publications

Inconsistency-Tolerant Query Answering in Ontology-Based Data Access

Inconsistency-Tolerant Query Answering in Ontology-Based Data Access

RDF 1.1: Knowledge Representation and Data Integration Language for the Web

Ultrawrap: SPARQL Execution on Relational Data

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