Computational Inductive Definability
It is shown that over any countable first-order structure, IND programs with dictionaries accept exactly the Pi-1-1 relations. This extends a result of Harel and Kozen (1984) relating IND and Pi-1-1 over countable structures with some coding power, and provides a computational analog of a result of Barwise, Gandy, and Moschovakis (1971) relating the Pi-1-1 relations on a countable structure to a certain family of inductively definable relations on the hereditarily finite sets over that structure.
computer science; technical report
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