[COG] Media type

Sean Gillies sean at mapbox.com
Wed Jul 24 13:05:55 PDT 2019

Matthias, Vincent:

A boolean mime type parameters is not the way to do this. Defining whether
"cloud-optimized=false" has any meaning is just the first weird detail that
would have to be handled. Something like "profile=cog" would be better and
would be open to other profiles.

Debates about the name of the new parameter may be moot because TIFF has
registered only the "application" parameter:
https://www.iana.org/assignments/media-types/image/tiff and according to
Mark Nottingham [2] third-party parameters are seen to have the potential
to break the internet [2]. But maybe IANA will be fine with it in 2019.

If a new parameter were not an option, a "geotiff-cog" value for the
application parameter would be consistent with the TIFF spec and IANA
registration and is worth a consideration. "geotiff" is also a completely
new parameter value and practically no software understands what it means
right now. There's a small window perhaps to mint a second parameter value
and get all the software that would implement "application=geotiff" on
board with "geotiff-cog" (or whatever).

Sidebar: I feel like "cloud-optimized geotiff" is pretty vague about the
implementation and "cog" even more so. If this sub type were to be
formalized, I'd hope we could come up with something more technically clear
and less buzzy like "http optimized" or "direct access".

[1] https://tools.ietf.org/html/rfc6906
[2] https://www.mnot.net/blog/2012/04/17/profiles, comment on Thursday,
April 19 2012 at 5:35 AM

On Wed, Jul 24, 2019 at 12:46 PM Vincent Sarago <vincent.sarago at gmail.com>

> Thanks Matthias,
> I’m +1 on `image/tiff; application=geotiff; cloud-optimized=true`
> > Le 24 juill. 2019 à 13:35, Matthias Mohr <m.mohr at uni-muenster.de> a
> écrit :
> >
> > Dear all,
> >
> > the GeoTiff SWG decided on a media type for GeoTiff: image/tiff;
> application=geotiff
> > See
> https://github.com/opengeospatial/geotiff/issues/34#issuecomment-514078289
> >
> > Based on the assumption that IANA accepts it, I'm wondering whether COGs
> could also get a recommended media type now.
> >
> > Two proposals from my side:
> > - image/tiff; application=geotiff; cloud-optimized=true
> > - image/tiff; application=geotiff; cog=true
> >
> > What do you think?
> >
> > Having a recommendation would be very helpful for STAC and openEO, for
> example.
> >
> > Best,
> > Matthias

Sean Gillies
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