Greetings,

I have some questions that came up as I added GIFTI surface support in SUMA. The surface I used for testing was
Human.colin.Cerebral.R.FIDUCIAL.TLRC.711-2B.71723.surf.gii
1- What do we do with 'coordframe_id' ?
It seems to conflict with 'dataspace' and 'xformspace'.
2- 'comment', 'orientation', and 'pubmed_id' are not documented. So it is not clear what to do with them. I propose that application-specific metadata be named in an identifiable manner such as: 'caret-comment', 'caret-orientation', etc.
We should also discuss what ought to be done with non-standard metadata and data arrays. In the past we've touched on this issue but with little consideration of the implementation cost.
3-How do we know what to do with the DataArray of intent: NIFTI_INTENT_VECTOR in the surface mentioned above? Its purpose is unknown although I suspect it contains normals. But I can't really do much with it if I did not know what it was for. To follow up on Nick and Rick's thread about data inside surface files, I think we should only include data with a clearly defined intent. Otherwise, we can't tell what to propagate and what not to propagate. If I knew that the DataArray inside a surface file contained normals, then I would know to recompute them if I change the surfaces' geometry. Otherwise, the content of the DataArray would be incorrect with the newly deformed coordinates.
4-Lastly, I propose we use a specific string to state that a certain metadata is of unknown or unspecified value. Something like 'Unknown' perhaps?

cheers,
ziad