Since the 1909 work of Carathéodory, formulations of thermodynamics have gained ground which highlight the role of the the binary relation of adiabatic accessibility between equilibrium states. A feature of Carathéodory's system is that the version therein of the second law contains an ambiguity about the nature of irreversible adiabatic processes, making it weaker than the traditional Kelvin-Planck statement of the law. This paper attempts first to clarify the nature of this ambiguity, by defining the arrow of time in thermodynamics (...) by way of the Equilibrium Principle. It then argues that the ambiguity reappears in the important 1999 axiomatisation due to Lieb and Yngvason. (shrink)

The Region Connection Calculus (RCC theory) is a well-known spatial representation of topological relations between regions. It claims that the connection relation is primitive in the spatial domain. We argue that the connection relation is indeed primitive to the spatial relations, although in RCC theory there is no room for distance relations. We first analyze some aspects of the RCC theory, e.g. the two axioms in the RCC theory are not strong enough to govern the connection relation, regions in the (...) RCC theory cannot be points, the uniqueness of the $$\iota $$ operation in the theory is not guaranteed, etc. To solve some of the problems, we propose an extension to the RCC theory by introducing the notion of region category and adding a new axiom which governs the characteristic property of the connection relation. The extended theory is named as RCC++. We support the claim that the connection relation is primitive to spatial domain by showing how distance relations, size relations are developed in RCC++. At last we revisit a sub-family of un-intended models in RCC theory, argue that RCC++ is more suitable than RCC with regards to its original intended model, and discuss the representation limitation of the RCC, as well as RCC++. (shrink)