This page shows the corralation function of Wiener process X is $R(s,t)=\min (s,t)$.
I've learned how to compute the corralation function of a process, but now encountered an inverse problem: to determined if a function is a corralation function of some process.
The problem gives $f(s,t)=\min{(s,t)}$ as an example. Surely I know that it is a corralation function referring to the page mentioned, but what if I don't know (or cannot find) the original process? Is there and procedure to determine this?