Add relation between different parametrizations?

[rlouf]

Examples that come to mind are the Binomial distribution and the Wald distribution (but there are so many others, see the Leemis chart for more examples). We will need to add new RV types for these distributions.

This could be very useful, for instance the Wald distribution in its usual form can be reparametrized to a form that belongs to the scale family, thus enabling new rewrites.

The "X is a special case of Y when ..." fall under this category, the difference being we don't need to introduce new types.