Question: PDE numeric with three independent variables

Hi !

Do you know how I can solve numerically a system of partial differential equation with Maple ? I've 3 variables : x,y,t and my system is :

EDP := [diff(s(x, y, t), t) = -.45*i(x, y, t)*s(x, y, t), diff(i(x, y, t), t) = .45*i(x, y, t)*s(x, y, t)-.2*i(x, y, t)-.7*(diff(i(x, y, t), x)+diff(i(x, y, t), y))]

f :=  1-g(x) ; g :=  piecewise(x = 20, .2, 0)
IBC := {s(0, y, t) = 1, s(x, y, 0) = f(x, y), i(x, y, 0) = g(x)}

But when I do : PDS := pdsolve(EDP, IBC, numeric), I get :
Error, (in pdsolve/numeric/process_PDEs) can only numerically solve PDE with two independent variables, got {x, y, t}

Moreover, I'd like to see in 3D the solutions :

Uplot1 := PDS:-plot(s(x, t), x = 0 .. 100, y = 0 .. 100, t = 0, color = red);
Uplot2 := PDS:-plot(i(x, t), x = 0 .. 100, y = 0 .. 100, t = 0, color = blue);
Uplot3 := PDS:-plot(s(x, t), x = 0 .. 100, y = 0 .. 100, t = 10, color = red);
Uplot4 := PDS:-plot(i(x, t), x = 0 .. 100, y = 0 .. 100, t = 10, color = blue);
Uplot5 := PDS:-plot(s(x, t), x = 0 .. 100, y = 0 .. 100, t = 24, color = red);
Uplot6 := PDS:-plot(i(x, t), x = 0 .. 100, y = 0 .. 100, t = 24, color = blue);
Uplot9 := PDS:-plot(s(x, t), x = 0 .. 100, y = 0 .. 100, t = 31, color = red);
Uplot10 := PDS:-plot(i(x, t), x = 0 .. 100, y = 0 .. 100, t = 31, color = blue)

But it show nothing :/

Thanks for your help !