I am very familiar with problems of the form
y'(x) = f(r; x, y), y(a)=y0, y(b)=y1
where r is a parameter to be estimated using the boundary values.
But apart from this situation, has anyone found other reasons why we should a boundary value problem of the form
y'(x) = f(x, y), y(a)=y0, y(b)=y1
To me, I think a BVP should be of second-order or higher. So I think the simplest BVP should be of the form
y''(x)=f(x,y,y'), y(a)=y0, y(b)=y1