Tannaka-Krein duality for compact groupoids III, duality theory

In a series of papers, we have shown that from the \repn theory of a compact groupoid one can reconstruct the groupoid using the procedure similar to the Tannaka-Krein duality for compact groups. In this part we introduce the Tannaka groupoid of a compact groupoid and show how to recover the original groupoid from its Tannaka groupoid.