Category theory as coherently constructive lattice theory : an illustration
RC Roland Backhouse, Mll Marcel Bijsterveld · 1994
Dijkstra and Scholten have formulated a theorem stating that all disjunctivity properties of a predicate transformer are preserved by the construction of least prefix points. An alternative proof of their theorem is presented based on two fundamental fixed point theorems, the abstraction theorem and the fusion theorem, and the fact that suprema in a lattice are defined by a Galois connection. The abstraction theorem seems to be new; the fusion theorem is known but its importance does not seem to be fully recognised. The abstraction theorem, the fusion theorem, and Dijkstra and Scholten's theorem are then generalised to the context of category theory and shown to be valid. None of the theorems in this context seems to be known, although specific instances of Dijkstra and Scholten's theorem are known. The main point of the paper is to discuss the process of drawing inspiration from lattice theory to formulate theorems in category theory (first advocated by Lambek in 1968). W...