4,809 research outputs found
Inconsistency-tolerant Query Answering in Ontology-based Data Access
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
A General Modifier-based Framework for Inconsistency-Tolerant Query Answering
We propose a general framework for inconsistency-tolerant query answering
within existential rule setting. This framework unifies the main semantics
proposed by the state of art and introduces new ones based on cardinality and
majority principles. It relies on two key notions: modifiers and inference
strategies. An inconsistency-tolerant semantics is seen as a composite modifier
plus an inference strategy. We compare the obtained semantics from a
productivity point of view
Information sharing performance management: a semantic interoperability assessment in the maritime surveillance domain
Information Sharing (IS) is essential for organizations to obtain information in a cost-effective way. If the
existing information is not shared among the organizations that hold it, the alternative is to develop the necessary
capabilities to acquire, store, process and manage it, which will lead to duplicated costs, especially unwanted if
governmental organizations are concerned. The European Commission has elected IS among public administrations
as a priority, has launched several IS initiatives, such as the EUCISE2020 project within the roadmap for developing the maritime Common Information Sharing Environment (CISE), and has defined the levels of interoperability essential
for IS, which entail Semantic Interoperability (SI). An open question is how can IS performance be managed?
Specifically, how can IS as-is, and to-be states and targets be defined, and how can organizations progress be
monitored and controlled? In this paper, we propose 11 indicators for assessing SI that contribute to answering these
questions. They have been demonstrated and evaluated with the data collected through a questionnaire, based on the
CISE information model proposed during the CoopP project, which was answered by five public authorities that require
maritime surveillance information and are committed to share information with each other.Postprint (published version
Inconsistency Handling in Ontology-Mediated Query Answering: A Progress Report
International audienceThis paper accompanies an invited talk on inconsistency handling in OMQA and presents a concise summary of the research that has been conducted in the area
Complexity of Inconsistency-Tolerant Query Answering in Datalog+/- under Cardinality-Based Repairs
This is the author accepted manuscript. The final version is available from Association for the Advancement of Artificial Intelligence (AAAI) via the link in this recordQuerying inconsistent ontological knowledge bases is an important
problem in practice, for which several inconsistencytolerant
query answering semantics have been proposed, including
query answering relative to all repairs, relative to
the intersection of repairs, and relative to the intersection of
closed repairs. In these semantics, one assumes that the input
database is erroneous, and the notion of repair describes a
maximally consistent subset of the input database, where different
notions of maximality (such as subset and cardinality
maximality) are considered. In this paper, we give a precise
picture of the computational complexity of inconsistencytolerant
(Boolean conjunctive) query answering in a wide
range of Datalog± languages under the cardinality-based versions
of the above three repair semantics.This work was supported by the Alan
Turing Institute under the UK EPSRC grant EP/N510129/1,
and by the EPSRC grants EP/R013667/1, EP/L012138/1,
and EP/M025268/1
Querying and Repairing Inconsistent Prioritized Knowledge Bases: Complexity Analysis and Links with Abstract Argumentation
In this paper, we explore the issue of inconsistency handling over
prioritized knowledge bases (KBs), which consist of an ontology, a set of
facts, and a priority relation between conflicting facts. In the database
setting, a closely related scenario has been studied and led to the definition
of three different notions of optimal repairs (global, Pareto, and completion)
of a prioritized inconsistent database. After transferring the notions of
globally-, Pareto- and completion-optimal repairs to our setting, we study the
data complexity of the core reasoning tasks: query entailment under
inconsistency-tolerant semantics based upon optimal repairs, existence of a
unique optimal repair, and enumeration of all optimal repairs. Our results
provide a nearly complete picture of the data complexity of these tasks for
ontologies formulated in common DL-Lite dialects. The second contribution of
our work is to clarify the relationship between optimal repairs and different
notions of extensions for (set-based) argumentation frameworks. Among our
results, we show that Pareto-optimal repairs correspond precisely to stable
extensions (and often also to preferred extensions), and we propose a novel
semantics for prioritized KBs which is inspired by grounded extensions and
enjoys favourable computational properties. Our study also yields some results
of independent interest concerning preference-based argumentation frameworks.Comment: 27 pages. To appear in the 17th International Conference on
Principles of Knowledge Representation and Reasoning (KR 2020) without the
appendi
Dealing with Inconsistencies and Updates in Description Logic Knowledge Bases
The main purpose of an "Ontology-based Information System" (OIS) is to provide an explicit description of the domain of interest, called ontology, and let all the functions of the system be based on such representation, thus freeing the users from the knowledge about the physical repositories where the real data reside. The functionalities that an OIS should provide to the user include both query answering, whose goal is to extract information from the system, and update, whose goal is to modify the information content of the system in order to reflect changes in the domain of interest.
The "ontology" is a formal, high quality intentional representation of the domain, designed in such a way to avoid inconsistencies in the modeling of concepts and relationships. On the contrary, the extensional level of the system, constituted by a set of autonomous, heterogeneous data sources, is built independently from the conceptualization represented by the ontology, and therefore may contain information that is incoherent with the ontology itself.
This dissertation presents a detailed study on the problem of dealing with inconsistencies in OISs, both in query answering, and in performing updates. We concentrate on the case where the knowledge base in the OISs is expressed in Description Logics, especially the logics of the DL-lite family. As for query answering, we propose both semantical frameworks that are inconsistency-tolerant, and techniques for answering unions of conjunctive queries posed to OISs under such inconsistency-tolerant semantics. As for updates, we present an approach to compute the result of updating a possibly inconsistent OIS with both insertion and deletion of extensional knowledge
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