You know, in a Postproduction software like AfterFX, the workspace is X,Y, while the depth is Z. In 3D realm, that depth would be Y.
On the other hand, 3D software like Maya uses the Y as Up-Axis as standard, as opposed to, let's say 3ds max. Und the cool thing is, you can even revert that (y-z exchange). So what's the point Oerwinde?
In the end, it's up to the developer/viewer how you want to setup the axis. There's no clear standard.