This question already has an answer here:
I was curious about finding users that have higher reputation on SE sites other than stackoverflow.
I'm kind of fuzzy on what I want to do, but my hypothesis is that ... people who are involved in SE but not very involved in SO are rare.
So anyway, I went to http://data.stackexchange.com/stackoverflow/query/new and immediately realized that I need to limit my query to a single site.
a) Is it possible to query multiple sites in some way that I've overlooked? b) If not, is this feature planned? c) If not, then out of interest, what is missing for it to be implemented?