Measuring

[Eric Douglas]

How does Fop measure?
If I put a tag in my .fo for <fo:block-container position="absolute"
left= ...
Does it measure in pixels / points (are they the same thing?)?
Do I need to specifiy?  left="10px" or just left="10"?
It appears to work the same with or without a unit of measure, assuming
the page measurement to be 72PPI, but I don't want to make an assumption
and be wrong later.