All great points/questions, thank you @asibbald! I’ll take them one at a time:
“with this function “ - which function is being referred to? Query? base? for_user?.
We do mean the base/0 function. I’ll clarify that in the next release 
“we name the concept of…” do you mean something like “we introduce the concept of…?”
What we mean here is that we are encapsulating the responsibility of the base query and giving it a name.
“…we provide one common way to build the foundation for all Demographic queries…” It’s not clear how we do this.
What we mean here is that the base/0 function provides this common functionality for the first step of writing any new query for demographics.
I think we can add some language to clarify this a bit.