Color space conversions to/from XYZ broken?

I have just started writing a plug-in in which I need to convert data from an RGB space to XYZ and back again. For this I am using the sPSColorSpace->Convert16 function.
Unfortunately, it seems that the conversions to and from XYZ are not performed correctly. I do not know exactly what *is* calculated, but XYZ it's not. One of the giveaways is that the result of the conversion depends on the color space of the RGB data, including the gamma. Instead, the XYZ values should be uniquely defined, independent of the source RGB space.
I have since created a work-around, by using the sPSColorSpace->Convert16 function to convert RGB values to Lab, and converting those to XYZ and back again with my own code. In this way, everything works as expected. However, it's unsatisfactory for two reasons: (1) a basic SDK function seems to be broken, and (2) my workaround is very slow, introducing 4(!) redundant nonlinear transforms per pixel.
Does anyone have similar or contrary experiences? And, assuming I haven't messed up, how should one go about notifying Adobe about this? Thanks in advance!
Simon

>XYZ is a device independent color space, not a transformation of RGB (like HSB).
That is exactly what I meant. Sorry for expressing myself poorly.
The test I did was as follows. I applied my filter as a smart filter to an RGB smart object. I then *converted* (not assigned) the RGB object to another color space using a relative colorimetric conversion. Because my filter operates in the XYZ space, the (visual) output should be unaffected by the color space conversion. Unfortunately, the output changed.
When I changed my filter to use Convert16 to convert to Lab (instead of XYZ) and back, and manually performed the Lab<->XYZ conversion, the (visual) output was indeed independent of the source color space.
My conclusion is that XYZ as calculated by the Convert16 function *is* a 'transformation of RGB', but, you are correct, it shouldn't be. The conversion does not properly account for the source RGB space.
Simon

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