dragger="box" or dragger="trackball"
and
technique="light" or technique="isosurface" or technique="iso" or technique="mip"
and
tf="transferfunctionfile.tf"
i.e.
<volume dragger="box">CardiacCT</volume>
<volume tf="colour.tf">CardiacCT</volume>
<volume technique="isosurface">CardiacCT</volume>