  ASD (Abstract Stone Duality) is a re-axiomatisation of general topology in
which the topology on a space is treated, not as an infinitary lattice, but as
an exponential object of the same category as the original space, with an
associated lambda-calculus. In this paper, this is shown to be equivalent to a
notion of computable basis for locally compact sober spaces or locales,
involving a family of open subspaces and accompanying family of compact ones.
This generalises Smyth's effectively given domains and Jung's strong proximity
lattices. Part of the data for a basis is the inclusion relation of compact
subspaces within open ones, which is formulated in locale theory as the
way-below relation on a continuous lattice. The finitary properties of this
relation are characterised here, including the Wilker condition for the cover
of a compact space by two open ones. The real line is used as a running
example, being closely related to Scott's domain of intervals. ASD does not use
the category of sets, but the full subcategory of overt discrete objects plays
this role; it is an arithmetic universe (pretopos with lists). In particular,
we use this subcategory to translate computable bases for classical spaces into
objects in the ASD calculus.
