1,124 research outputs found
Updating DL-Lite ontologies through first-order queries
In this paper we study instance-level update in DL-LiteA, the description logic underlying the OWL 2 QL standard. In particular we focus on formula-based approaches to ABox insertion and deletion. We show that DL-LiteA, which is well-known for enjoying first-order rewritability of query answering, enjoys a first-order rewritability property also for updates. That is, every update can be reformulated into a set of insertion and deletion instructions computable through a nonrecursive datalog program. Such a program is readily translatable into a first-order query over the ABox considered as a database, and hence into SQL. By exploiting this result, we implement an update component for DLLiteA-based systems and perform some experiments showing that the approach works in practice.Peer ReviewedPostprint (author's final draft
Towards Closed World Reasoning in Dynamic Open Worlds (Extended Version)
The need for integration of ontologies with nonmonotonic rules has been
gaining importance in a number of areas, such as the Semantic Web. A number of
researchers addressed this problem by proposing a unified semantics for hybrid
knowledge bases composed of both an ontology (expressed in a fragment of
first-order logic) and nonmonotonic rules. These semantics have matured over
the years, but only provide solutions for the static case when knowledge does
not need to evolve. In this paper we take a first step towards addressing the
dynamics of hybrid knowledge bases. We focus on knowledge updates and,
considering the state of the art of belief update, ontology update and rule
update, we show that current solutions are only partial and difficult to
combine. Then we extend the existing work on ABox updates with rules, provide a
semantics for such evolving hybrid knowledge bases and study its basic
properties. To the best of our knowledge, this is the first time that an update
operator is proposed for hybrid knowledge bases.Comment: 40 pages; an extended version of the article published in Theory and
Practice of Logic Programming, 10 (4-6): 547 - 564, July. Copyright 2010
Cambridge University Pres
Using Ontologies for Semantic Data Integration
While big data analytics is considered as one of the most important paths to competitive advantage of today’s enterprises, data scientists spend a comparatively large amount of time in the data preparation and data integration phase of a big data project. This shows that data integration is still a major challenge in IT applications. Over the past two decades, the idea of using semantics for data integration has become increasingly crucial, and has received much attention in the AI, database, web, and data mining communities. Here, we focus on a specific paradigm for semantic data integration, called Ontology-Based Data Access (OBDA). The goal of this paper is to provide an overview of OBDA, pointing out both the techniques that are at the basis of the paradigm, and the main challenges that remain to be addressed
A Typed Model for Linked Data
The term Linked Data is used to describe ubiquitous and emerging semi-structured data formats on the Web. URIs in Linked Data allow diverse data sources to link to each other, forming a Web of Data. A calculus which models concurrent queries and updates over Linked Data is presented. The calculus exhibits operations essential for declaring rich atomic actions. The operations recover emergent structure in the loosely structured Web of Data. The calculus is executable due to its operational semantics. A light type system ensures that URIs with a distinguished role are used consistently. The main theorem verifies that the light type system and operational semantics work at the same level of granularity, so are compatible. Examples show that a range of existing and emerging standards are captured. Data formats include RDF, named graphs and feeds. The primitives of the calculus model SPARQL Query and the Atom Publishing Protocol. The subtype system is based on RDFS, which improves interoperability. Examples focuss on the SPARQL Update proposal for which a fine grained operational semantics is developed. Further potential high level languages are outlined for exploiting Linked Data
On the evolution of the instance level of DL-lite knowledge bases
Recent papers address the issue of updating the instance level of knowledge
bases expressed in Description Logic following a model-based approach. One of
the outcomes of these papers is that the result of updating a knowledge base K
is generally not expressible in the Description Logic used to express K. In
this paper we introduce a formula-based approach to this problem, by revisiting
some research work on formula-based updates developed in the '80s, in
particular the WIDTIO (When In Doubt, Throw It Out) approach. We show that our
operator enjoys desirable properties, including that both insertions and
deletions according to such operator can be expressed in the DL used for the
original KB. Also, we present polynomial time algorithms for the evolution of
the instance level knowledge bases expressed in the most expressive Description
Logics of the DL-lite family
Reason Maintenance - State of the Art
This paper describes state of the art in reason maintenance with a focus on its future usage in the KiWi project. To give a bigger picture of the field, it also mentions closely related issues such as non-monotonic logic and paraconsistency. The paper is organized as follows: first, two motivating scenarios referring to semantic wikis are presented which are then used to introduce the different reason maintenance techniques
Belief Update in AgentSpeak-DL
In previous work (Moreira et al, DALT 2005) we proposed an extension
for the belief base of AgentSpeak agents
based on Description Logic (DL), aiming at enabling agent oriented
programming to cope with recently proposed
technologies for the Semantic Web. In such an extension an agent
belief base contains the
definition of complex concepts, besides specific factual knowledge.
The foreseen advantages are: (i) more expressive queries to the belief
base; (ii) a refined notion
of belief update, which considers consistency of a belief addition;
(iii) flexibility in plan searching allowed
by subsumption relation between concepts; and (iv) knowledge sharing
in a semantic web context (based on OWL).
Following this proposal an extension of the well know Agent Speak
interpreter, Jason, was presented by K
lapiscak and Bordini in DALT 2008. Among the interesting open issues
is how to deal with the addition of
beliefs which violates ontology consistency. In this work
discuss this problem related to
ABox updating in the context of AgentSpeak-DL
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