We present a generalization of the ideal model for recursive
polymorphic types. Types are defined as sets of terms instead of sets
of elements of a semantic domain. Our proof of the existence of types
as a solution of a fixpoint does not rely on metric spaces properties,
but instead uses the fact that the identity is the limit of projection
terms. This establishes a connection with the work of Pitts on
relational properties of domains. We suggest that the right
generalization of ideals are closed sets of terms defined by
orthogonality with respect to a set of contexts.
