>
>
> By: Richard Reynolds
>
> I think preserving unknown MetaData is actually a mistake.
>
>
> Having extra metadata to use in your local software package is
> okay. But the main point of GIFTI is as an exchange format.
>

I guess you can call GIFTI an exchange format. However, our intent
with Caret, and I believe the intent of others, is to replace our
"proprietary" file formats and use GIFTI as the standard file format
for Caret. Our vision is that a user can have ONE SET of files and
switch between neuroimaging software applications without having to do
any file format conversions.

> Also, having to write a new file B.gii from an existing file A.gii
> means having a reason to modify it.
>
> Those 2 points together mean that if the software that wrote file
> A.gii gets file B.gii back, they will have no idea what sorts of
> changes were done. Therefore, the assumptions it is likely to make
> based on the old copied MetaData may be invalid.
>
> For example, suppose Caret creates a dataset that has their own
> 'orientation' and 'coordframe_id' values set as MetaData. Now AFNI
> gets that file and performs some transformations on it, and writes
> it back out. Now someone takes it back to Caret.

Any of the caret specific metadata items that have GIFTI counterparts
will not be added to GIFTI data files written by Caret once the GIFTI
standard is finalized.

> If AFNI preserves that unknown metadata, it is probably garbage
> when it gets back to Caret. From Caret's perspective, who knows
> what hideous manipulations were performed in AFNI? At that point,
> only agreed upon GIFTI metadata is reliable.
>

Not necessarily. One item we sometimes place in metadata is a PubMed
Identifier that identifies the journal article that is the source of
the data. Even if this data is manipulated, the PubMed Identifier is
still pertains to the data.

> ---
>
> So anyway, if certain MetaData is essential for not mis-interpreting
> the dataset, then we need to use publicly agreed upon ways of passing
> it along.
>
> If that MetaData is not essential and is not understood by the
> reading software, then it should be thrown out. It can no longer be
> relied on to survive whatever computations are being performed.
>>
>
> My $0.02,
>
> - rick
>

First, and I believe this was decided at the in-person meeting in
D.C., unrecognized metadata should be passed thru as stated in the
GIFTI Format Document. Second, we should allow the users to add
metadata if they desire to do so, and, in this case, it is important
that it be preserved.

John Harwell