The present study focuses on a grammatical category called evidentiality. The primary meaning of evidentiality is concerned with information source. That is, it expresses whether something has been seen, heard or inferred. The aim here is to conduct a conceptual study of evidentiality in which use is made of formal tools. The fundamental intuition is that the distinction between ‘evidence’as ‘proof’and ‘evidentiality’as ‘to do with proof’is a crucial one. Evidentiality is a dynamic notion to be analysed through the use of (...) knowledge by the agents, a knowledge in action, which involves an in-coming state and an out-coming state that is typical of the transmission of information. We propose our own approach in which the dynamics of knowledge in action is grasped in the context of a dynamic epistemic logic. (shrink)

In van Benthem (2008), van Benthem proposes a dynamic consequence relation defined as${\psi _1}, \ldots,{\psi _n}{ \models ^d}\phi \,{\rm{iff}}{ \models ^{pa}}[{\psi _1}] \ldots [{\psi _n}]\phi,$where the latter denotes consequence in public announcement logic, a dynamic epistemic logic. In this paper we investigate the structural properties of a conditional dynamic consequence relation$\models _{\rm{\Gamma }}^d$extending van Benthem’s proposal. It takes into account a set of background conditions Γ, inspired by Makinson (2003) wherein Makinson calls this reasoning ‘modulo’ a set Γ. In the (...) presence of common knowledge, conditional dynamic consequence is definable from (unconditional) dynamic consequence. An open question is whether dynamic consequence is compact. We further investigate a dynamic consequence relation for soft instead of hard announcements. Surprisingly, it shares many properties with (hard) dynamic consequence. Dynamic consequence relations provide a novel perspective on reasoning about protocols in multi-agent systems. (shrink)