We propose a novel approach for performance prediction of OWL reasoners that selects suitable, small ontology subsets, and then extrapolates reasoner's performance on them to the whole ontology. We investigate intercorrelation of ontology features using PCA and discuss various error measures for performance prediction.

In this paper, we address the problem of applying AGM-style belief revision to non-classical logics. We discuss the idea of minimal change in revision and show that for non-classical logics, some sort of minimality postulate has to be explicitly introduced. We also present two constructions for revision which satisfy the AGM postulates and prove the representation theorems including minimality postulates.

In this work we study action theories of the situation calculus such that the initial KB is a generalized database with equality constraints (GFDBs). We show that GFDBs characterize the class of definitional KBs and that they are closed under progression. We also show that, under conditions, generalized projection queries can be decided based on an induced transition system and evaluation of local conditions over states.

Aggregative deontic detachment is a new form of deontic detachment that keeps track of previously detached obligations. We argue that it handles iteration of successive detachments in a more principled manner than the traditional systems do. To study this new form of deontic detachment, we introduce a'minimal' logic for aggregative deontic detachment, and we discuss various properties of the logic.

The paper develops a branching-time ontology that maintains the classical restriction of forward movement through a temporal tree structure, but permits the representation of paths in which one can perform inferences about time-travel scenarios. Central to the ontology is the notion of an agent embodiment whose beliefs are equivalent to those of an agent who has time-traveled from the future.

We propose a model of belief and intention change over the course of a dialogue, in the case where the decisions taken during the dialogue affect the possibly conflicting goals of the agents involved. We use Situation Calculus to model the evolution of the world and an observation model to analyze the evolution of intentions and beliefs. In our formalization, utterances, that only change the beliefs and intentions, are observations. We illustrate our formalization with the game of Werewolf.

We develop a clausal resolution-based approach for computing uniform interpolants of TBoxes formulated in the description logic ALC when such uniform interpolants exist. We also present an experimental evaluation of our approach and of its application to the logical difference problem for real-life ALC ontologies. Our results indicate that in many practical cases uniform interpolants exist and that they can be computed with the presented algorithm.

We tackle a long-standing open research problem and prove the decidability of query answering under the stable model semantics for guarded existential rules, where rule bodies may contain negated atoms, and provide complexity results. The results extend to guarded Datalog /- with negation, and thus provide a natural and decidable stable model semantics to description logics such as ELHI and DL-LiteR.

We provide a sound and complete axiomatization for a class of logics appropriate for reasoning about the rationality of players in games. Essentially the same axiomatization applies to a wide class of decision rules.

We examine several belief change operations in the light of Dynamic Logic of Propositional Assignments DL-PA. We show that we can encode in a systematic way update operations (such as Winslett's Possible Models Approach') and revision operations (such as Dalal's) as particular DL-PA programs. Every DL-PA formula being equivalent to a boolean formula, we obtain syntactical counterparts for all these belief change operations.