Same as AP, except we are promised that each existential quantifier has at most one 'yes' path, and each universal quantifier has at most one 'no' path.
Contains UP.
Defined in [NR98], where it was also shown that, even though AP = PSPACE, it is unlikely that the same is true for UAP, since UAP is contained in SPP.
[CGR+04] have also shown that UAPUAP = UAP, and that UAP contains Graph Isomorphism problem.
No class.