In this work we propose an encoding of Reiter’s Situation Calculus solution to the frame problem into the framework of a simple multimodal logic of actions. In particular we present the modal counterpart of the regression technique. This gives us a theorem proving method for a relevant fragment of our modal logic.

During a dialogue, agents exchange information with each other and need thus to deal with incoming information. For that purpose, they should be able to reason effectively about trustworthiness of information sources. This paper proposes an argument-based system that allows an agent to reason about its own beliefs and information received from other sources. An agent's beliefs are of two kinds: beliefs about the environment and beliefs about trusting sources . Six basic forms of trust are discussed in the paper (...) including the most common one on sincerity. Starting with a base which contains such information, the system builds two types of arguments: arguments in favour of trusting a given source of information and arguments in favour of believing statements which may be received from other agents. We discuss how the different arguments interact and how an agent may decide to trust another source and thus to accept information coming from that source... (shrink)

Trust may have many different informal definitions. In this work, formal definitions are proposed in Modal Logic in order to have clear rules for reasoning about trust. We start from trust in some properties of an information source, like sincerity, competence or vigilance, about a given proposition. Then, this definition is extended to trust about all the propositions which are about a given topic. A further extension is about all the propositions which inform about a given individual. Specific logics are (...) presented for reasoning about the fact that a given proposition is about a given topic and for reasoning about the fact that a proposition informs about a given individual. At the end, we give a brief extension to qualitative graded trust. (shrink)

We propose a translation into Modal Logic of the ideas that formalise belief change in the Situation Calculus. This translation is extended to the case of revision. In the conclusion is presented a set of open issues.

This chapter contains sections titled: An Approach to the Logic of Action Normative Act Positions.

The interactions among the components of a biological system can be given a logical representation that is useful for reasoning about them. One of the relevant problems that may be raised in this context is finding what would explain a given behaviour of some component; in other terms, generating hypotheses that, when added to the logical theory modelling the system, imply that behaviour. Temporal aspects have to be taken into account, in order to model the causality relationship that may link (...) the behaviour of a given component to that of another one. This paper presents a hypothesis generation method for linear temporal logic theories whose formulae have a restricted syntactic form, which is however sufficient to model cellular and molecular interactions, as they are often represented by biologists. The method exploits the duality between hypothesis generation and consequence finding, and can therefore be also used to infer the consequences of a given fact. It is based on a resolution system proposed by Cavalli and Fariñas del Cerro in 1984. (shrink)

In this paper we attempt to supply answers to questions of the following kinds: How are database Integrity Constraints to be characterised formally? How is the concept of violation of an IC to be understood? What is the epistemic status of an IC? Following an analysis of the standard treatment of ICs, based on a simple example, we recall how Reiter provided a clear definition of the epistemic status of ICs. On Reiter's approach, ICs are implicitly supported by statements that (...) are guaranteed to be true; this property is explicit in the standard view of ICs, and we proceed to show how the standard view of ICs may be refined in the light of Reiter's work. We then supply formal definitions of the properties of Validity and Completeness which have to be enforced using ICs, and we give general formal results concerning techniques which can be used to check these properties. We propose to split the overall information involved in Integrity Checking into three components called DB, SAF and IC. DB represents a description of the world that is not necessarily guaranteed to be correct; SAF represents the information about the world that is guaranteed to be true, and which is used to check violations of Validity or Completeness; and IC defines the parts of DB for which the properties of Validity or Completeness must be enforced. (shrink)

The paper presents a logical framework for the representation of interactions between institutional agents, human agents and software agents. A case study is used to analyze how obligations on institutional agents are “propagated” to human and software agents, and how actions performed by these agents count as actions that satisfy the obligations imposed to institutional agents. It is shown that the relationship between the different kinds of obligations and actions can be represented in terms of the concept of “count as” (...) proposed by Searle, of role and of causality. The logical framework focus on those three concepts. (shrink)

The communication process is analysed on the basis of the notions of trust and agency. The aim of the paper is to clarify the role played by causality on the one hand and the role played by logical consequences of assumptions about trust in information sources on the other hand. The first part is informal and the second part refers to the logical framework of modal logic though it requires a quite limited background in this area.