  Motivated by structural issues in the AdS-CFT correspondence, the theory of
generalized free fields is reconsidered. A stress-energy tensor for the
generalized free field is constructed as a limit of Wightman fields. Although
this limit is singular, it fulfils the requirements of a conserved local
density for the Poincar'e generators. An explicit "holographic" formula
relating the Klein-Gordon field on AdS to generalized free fields on Minkowski
space-time is provided, and contrasted with the "algebraic" notion of
holography. A simple relation between the singular stress-energy tensor and the
canonical AdS stress-energy tensor is exhibited.
