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Four-valued description logic has been proposed to reason with description logic based inconsistent knowledge bases, mainly ALC. This approach has a distinct advantage that it can be implemented by invoking classical reason-ers to keep the same complexity as classical semantics. In this paper, we further study how to extend the four-valued semantics to more(More)
Role-based access control (RBAC) is recognized as an excellent model for access control in large-scale networked applications. Formalization of RBAC in a logical approach makes it feasible to reason about a specified policy and verify its correctness. We propose a formal-ization of RBAC by the description logic language ALCQ. We also show that the RBAC(More)
The wide scale usage of OWL for the formalization of real-world ontologies is currently influenced by important limitations which concern both its expressivity and the efficiency of OWL specific reasoning tools. While the expressivity limitations may be overcame by extending the OWL language (e.g. with rules), the reasoning with such heterogeneous knowledge(More)
Measuring inconsistency degrees of inconsistent knowledge bases is an important problem as it provides context information for facilitating inconsistency handling. Many methods have been proposed to solve this problem and a main class of them is based on some kind of paraconsistent semantics. In this paper, we consider the computational aspects of(More)
Inconsistency handling in expressive description logics is an important problem because inconsistency may naturally occur in an open world. In this paper, we first present the quasi-classical semantics for description logic SHIQ, which is based on quasi-classical logic. We show that this semantics can be used to deal with inconsistency and that it is(More)
In this paper, we present an approach for measuring inconsistency in a knowledge base. We first define the degree of inconsistency using a four-valued semantics for the description logic ALC. Then an ordering over knowledge bases is given by considering their inconsistency degrees. Our measure of inconsistency can provide important information for(More)
As a vision for the future of the Web, the Semantic Web is an open, constantly changing and collaborative environment. Hence it is reasonable to expect that knowledge sources in the Semantic Web contain noise and inaccuracies. However, as the logical foundation of Ontology Web Language in the Semantic Web, description logics fail to tolerate inconsistent(More)
Measuring inconsistency in knowledgebases has been recognized as an important problem in many research areas. Most of approaches proposed to measure inconsistency are based on paraconsistent semantics. However, very few of them provide efficient algorithms for implementation. In this paper, we first give the four-valued semantics for first-order logic and(More)