Categories of contexts

Abstract

Morphisms between (formal) contexts are certain pairs of maps, one between objects and one between attributes of the contexts in question. We study several classes of such morphisms and the connections between them. Among other things, we show that the category CLc of complete lattices with complete homomorphisms is (up to a natural isomorphism) a full reflective subcategory of the category of contexts with so-called conceptual morphisms; the reflector associates with each context its concept lattice. On the other hand, we obtain a dual adjunction between CLc and the category of contexts with so-called concept continuous morphisms. Suitable restrictions of the adjoint functors yield a categorical equivalence and a duality between purified contexts and doubly based lattices, and in particular, between reduced contexts and irreducibly bigenerated complete lattices. A central role is played by continuous maps between closure spaces and by adjoint maps between complete lattices.