In the 80's, André Haefliger introduced the problem of compact realization for foliations -- which is still open, and gave a sufficient condition for realization, the compact generation of the holonomy pseudogroup. We introduce a Morita-invariant notion of compact generation for general Lie groupoids, extending Haefliger's compact generation for pseudogroups, which provides Haefliger's condition for foliation groupoids in a very natural way.
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