The purpose of this paper is to
extend the theory of Hilbert spaces with kernel function to obtain first the kernel
function of any subspace described as the intersection of the nullspaces of countably
many continuous linear functionals, and secondly the solution of minimum norm to
interpolation problems involving countably many linear side conditions. The results
are then applied to obtain in §1 a class of pseudoconformally invariant functions in
Cn and in §2 further results on the classical interpolation problem involving
pointwise evaluation.