A precise and general notion of manifold
  We give a completely formalized definition of a notion of " general manifold ". It turns out that " gluing data " form an equivalence-partially ordered set (e-pos), which is a special instance of an ordered groupoid. We state and prove reconstruction theorems, allowing to reconstruct general manifolds and their mor-phisms from such gluing data. To describe morphisms between manifolds, the notion of natural relations between groupoids is introduced, which emphasizes the close analogy with natural transformations of general category theory. 
Wolfgang Bertram
math.CT math.DG