[fitsbits] FITS Binary Table Proposals

[Thomas McGlynn]

They look pretty good to me, but here are a few comments.

Some tiny editorial points in the TDIM convention.
I'd just make it
    8.3.6 Multidimensional Arrays
This is now the standard way to define multidimensional arrays in FITS binary tables.

For the second sentence
    Any column with a dimensionality ... has ...
not "will have" since we use present tense everywhere else in the discussion.

Typo in "see Section[m] 8.3.5"


Similary for the Variable length arrays...

    8.3.5 Variable Length Arrays

I'm not sure that the last sentence to the third paragraph means
anything, i.e., "Other established..." so I'd get rid
of it.

There is an upper limit to the size of the stored array: the maximum
value of a 4 byte integer

A few things that should probably be tied down specifically that are
currently a bit loose:

1. Are the sizes and offsets signed integers or unsigned?
If there were defined to be unsigned integers they could handle
objects twice as large and we wouldn't need to worry about
negative offsets.

2. Can THEAP be negative?   The possibility of a negative 'gap'
is not explicitly forbidden, but probably should be.   Or
do we want to allow reuse of data from the table as variable
length data.  One could make interesting structures...  Even if
we permit negative THEAP's (which I suspect will not be the case)
presumably it needs to be restricted to staying within the
current Data unit.


		Tom McGlynn

William Pence wrote:
> In response to the comments received so far during the official Public 
> Comment Period on the proposals to incorporate the TDIMn and variable 
> length array conventions for FITS binary tables into the official FITS 
> Standard, I have created new detailed drafts of the proposals which are 
> available at
> 
> http://fits.gsfc.nasa.gov/bintable_proposals.html
> 
> In particular, these new drafts contain the following changes:
> 
> 1. As recommended by Tom McGlynn, the drafts now specify precisely the 
> wording that should be inserted into the FITS Standard.
> 
> 2. As recommended by Bob Garwood, the TDIMn convention has been extended 
> slightly to allow the size of the array as given by the product of the 
> dimensions to be "less than or equal" to the allocated array size in the 
> FITS file.
> 
> 3. As recommended by Francois Ochsenbein, a cautionary phrase has been 
> added to warn users that the variable length array convention may 
> present difficulties for applications that ingest FITS files via a 
> sequential input stream.
> 
> The wording of these proposals may still not be optimal, so any further 
> suggestions are welcome.
> 
> 
> Bill Pence