 
Summary: A Per Model of Polymorphism
and Recursive Types
M. Abadi \Lambda G. D. Plotkin y
1 Synopsis
A model of Reynolds' polymorphic lambda cal
culus is provided, which also allows the recursive
definition of elements and types. The technique
is to use a good class of partial equivalence re
lations over a certain cpo. This allows the com
bination of inverselimits for recursion and inter
section for polymorphism.
2 Introduction
The ideal model provides an interpretation for a
rich type system, with polymorphism and recur
sion [12], but not a model of the typed –calculus.
In search for a satisfactory semantics for –calculi
with recursive and polymorphic types, it seems
natural, then, to consider partial equivalence re
lations (pers) instead of ideals. As ideals are cer
tain subsets of a universal domain D, we replace
