Is there a utility to deal with Spatial transforms?

I notice that there is a TransformMatrix class, but where it's created, it's always created as one matrix, and then the three values are filled in from the spatial: rotation, translation, scale. Wouldn't it be simpler to just have a single constructor, or, if math can't link against scene, at least a function in Spatial to do that?

Also, I can't find a function to return the inverse of a TransformMatrix, nor a function to return a Matrix4f from a TransformMatrix. What I want to do is know the relative transform between Node A and Node B, and the easiest way to do that is to multiply the world transform of Node B by the inverse of the world transform of Node A. This is a pretty common thing to want to do when using a scene graph, but I just can't find a simple one-line way of doing it! (or even a two-line way)