Literature on surrogates with discrete variables

[tusharg]

Hello,

I want to construct surrogate models of discrete variables.

I would highly appreciate if you direct me to some relevant literature or softwares.

Also I would like to solicit your personal experiences with such problems.

Thanks,
Tushar

[haftka]

If the discrete variables are closely spaced (e.g., integers from 1 to 100) any old surrogate will do. Is this a question about what DOE to use?

Rafi