Originally posted by Mathieu Coursolle: The intention here was to to have a complete description of all the data that is included in the file.  What data you choose to put in is up to you.  The ml variable has to exist for every data vector in the file, and specifies information about that vector of data (it refers to a source position, a detector position, and a wavelength) but it does not have to be a complete set of possible source detector pairs (it is not required that you record source detector data for pairs that are too far apart to have useful information, or for lasers that are off, etc..  The only requirement is that if it's in the file, it needs to be completely described). Yes.  We'll revise the description to say that.
That sounds like a good idea; we'll have to think about what geometries would make the most sense ("scanner anatomic" is probably not relevant, but "MNI", "Talairach", maybe "10-20" might be good choices-  we'd have to decide how the last would be implemented). The underlying file is an HDF5 file, which will take care of the endianness.
There are some places where we have specified a data type, but I think in the absence of a clear description, we should probably assume "double".  David, what do you think?