[fitsbits] Start of the 'INHERIT' Public Comment Period

[Rob Seaman]

William Pence wrote:

> Maybe I'm missing your point, but I don't see how that paper can be  
> interpreted as an endorsement of the inherit convention.

It can't.  The fact that the paper attempted to force a particular  
outcome - that primary HDUs not be empty - and that empty primary  
HDUs have instead become widespread, respected usage was my  
(admittedly obscure) point.

A FITS file is either conforming or it isn't.  Nothing requires that  
HDUs not be empty, for whatever purpose.  Users are also permitted to  
define new keywords with new interpretations.

In this case, fundamental goals of DB normalization drive the  
existence of a primary header to contain keywords that apply to all  
other extensions in a file.  There are reasons more basic than not  
consuming an additional N*80 bytes (1.2 KB for each Mosaic keyword)  
for not duplicating redundant keywords.

> Some might suggest that with the abundance of low cost disk space  
> that is now available, the inherit convention is trying to fix a  
> non-problem.

The diskspace may be a non-problem (although this is a quirky opinion  
coming from a FITS compression stalwart :–), but the underlying  
question is about the purpose of registering conventions in the first  
place.

I would have thought that the key goal was to collect descriptions of  
local usage, not to vet long-established usage against esthetic  
criteria.  By insisting on the latter, the danger is that conventions  
will go unregistered, perhaps undocumented.  Is this a preferred  
outcome?

If the warning:

	"These conventions are not necessarily endorsed by the IAU FITS  
Working Group."

is not deemed strong enough, how about labeling *all* of the  
conventions with something snarkier?  There is nothing demonstrably  
less conforming to the standard about INHERIT than any other convention.

I also suggest deleting the entire section "Practical Considerations"  
from http://fits.gsfc.nasa.gov/registry/inherit/ 
fits_inheritance.txt.  It amounts to nothing more than stating that  
unusual things might happen if files are run through software that  
doesn't know about the particular convention.  This applies to all  
conventions (and all software), and it seems to this observer that  
INHERIT is rather more user friendly in such a case than most.

Rob

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