The Oyster system at Edinburgh University's AI department is based on the Nuprl type theory; it currently uses the logic from Nuprl 3. This is one of the systems that Alan Bundy's research group at Edinburgh uses to study proof planning. They call it the Oyster program development system. Alan Bundy said in his paper Automatic Guidance of Program Synthesis Proofs,

"We have built our own version of Nuprl, which we call Oyster. It differs from Nuprl by being implemented in Prolog rather than Lisp, being considerably smaller and more transparent, and using Prolog rather than ML as the tactic language."