Transformation Matrix - coordinate system?

Hello,

I'm currently trying to to build some Python/JavaScript combination that
will render simple Ipe figures into SVGs, basically. This is more or
less straightforward so far, but I have trouble figuring out the
coordinate system used for the transformation matrix that can be applied
to all objects.

I tried just amending the matrix to a standard
2D-Rotation/Translation-Matrix by appending a row "0,0,1" to it and then
multiplying it to the coordinates, but then the resulting coordinates
are way off. I assume that the matrix is to be read in a object
coordinate system, but how do I get the translation from the page
coordinate system into the object coordinate system?

It would be awesome if someone could shed some light on this. Since I
could not find any documentation on this, I promise to whip up a
documentation-pullrequest or at least an entry to the wiki as soon as I
understand it. ;)

Thanks in advance,

Lukas