Modal logics are coalgebraic

Applications of modal logics are abundant in computer science, and a large number of structurally different modal logics have been successfully employed in a diverse spectrum of application contexts. Coalgebraic semantics, on the other hand, provides a uniform and encompassing view on the large variety of specific logics used in particular domains. The coalgebraic approach is generic and compositional: tools and techniques simultaneously apply to a large class of application areas and can moreover be combined in a modular way. In particular, this facilitates a pick-and-choose approach to domain specific formalisms, applicable across the entire scope of application areas, leading to generic software tools that are easier to design, to implement, and to maintain. This paper substantiates the authors' firm belief that the systematic exploitation of the coalgebraic nature of modal logic will not only have impact on the field of modal logic itself but also lead to significant progress in a number of areas within computer science, such as knowledge representation and concurrency/mobility

Perception and Testimony as Data Providers

Assuming that the sceptical challenge might be either bypassed or answered, this still leaves unspecified how high-quality information about the external world is acquired. In this paper, I will argue that, if knowledge is accounted information, then when we apply this definition to the analysis of perceptual knowledge and knowledge by testimony (the only two sources of information about the external world), the result is that both qualify as data providers.Peer reviewe