2004.10.01 07:22 "[Tiff] BigTIFF extension issue", by Joris Van Damme

People,

The current proposal for BigTIFF mentions 'tf8' as extension for BigTIFF. I'd like your opinions on using 'tif' as an extension, instead. If feel this might be more appropriate, for these reasons:

• The specification of BigTIFF largely relies on the TIFF specification. I can't see how it can be more then just a few pages on top of the 121 page TIFF specification. This seems to support that BigTIFF is much more a new version of TIFF, rather then a new file format.
• The same statement seems supported by our future codec works to support BigTIFF. Rather then building a new codec, it'll involve changing the existing one, and needed changes will probably not be very extensive.
• The 'new version' statement seems to also be supported by the changes in what is commonly said to be the version number in the TIFF header. 42 becomes 43. Again, BigTIFF seems much more of a new version of TIFF, not really a new file format.
• I believe there are precedents. GIF at one time went through a change that was quite drastic. It nevertheless did not change name or extension, version number 87a became 89a (IIRC), but gif remained gif. Jpeg at one time added the 'progressive jpeg' feature. But extension did not change. I believe that probably the change in TIFF, when it acquired the tiles scheme and added this to the strips scheme, was probably a change that was comparable in size. But the file format stayed labelled the same 'TIFF', and the extension remained the same. Rather, people talked about 'tiled' tiffs and such much like we now talk about 'Classic TIFF' and 'BigTIFF'.
• Where file format name and extension really does change, changes in specification are much more huge. In fact, most often, it's not the same specification basis - not the same file format. I'm thinking of jpg/jp2, and png/mng. Png and Mng belong to the same family, but the difference between them is much more huge then the difference between Classic TIFF and BigTIFF. Same goes for Jpeg and Jpeg2000.
• I believe average users often have a hard time finding their way in the confusing Fangorn forest of file format. Let's help 'em. What they know about files labelled '.tif', pretty much goes for our new BigTIFF, too. So let's stick with '.tif'.
• One final good reason to stick with '.tif', is, I believe, the acceptance of the file format, and the support for it. If/when a file called 'yada.tif' does not work in an application XY SuperViewer that claims to support TIFF, users are more likely to contact the XY vendor. This one may then reply 'OK, I see this is a BigTIFF, we don't yet support that', but the vendor will at least be made aware of the user needs, and the vendor's psychology implies that he will fear SuperViewer might become known as having inadequate TIFF support. But if/when a file called 'yada.tf8' does not work in XY SuperViewer, a whole other scenario is much more likely. The user will scratch his head, wonder 'what is .tf8 in the first place' for half a second, and next either forget about it, or go looking for another viewer. The XY vendor is most probably not being nagged. I thus believe that it is important to stick with the extension '.tif' in order to facilitate growing support for BigTIFF.

Joris Van Damme
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