[fitsbits] start of Public Comment Period on the column limits convention

[Tom McGlynn]

I've thought of a few more questions on this proposal that are unclear 
at least to me:

   - Can these keywords be used to refer to columns that are vector 
valued.  If so does
the limit apply to each element of the vector?  The analogy to BUNIT 
suggests yes,
but the wording regarding 'same type data type as physical values' is 
ambiguous.  If the plural refers to the rows separately then this is 
precluded, but if the plural applies within the row, then vectors may be 
allowed.
   - Should there be a mechanism to allow for min/max values of 
strings?  Is it illegal
to extend these keywords to use for non-integer/floating point data?  
(i.e., strings, complex,
bit, boolean)?   I think the answer to that is yes, but I believe it 
should be explicit.
   - Is it legal to have  an integer limit and a floating point column?  
Vice versa?
   - If limits on vector valued columns are allowed, then the situation 
for complex values is slightly more confused.  Do we allow a real limit 
which applies to each of the components of the complex in the same 
fashion as it would apply to each element of a vector?
   - The language suggested in 7.2.2 might suggest that the use of these 
keywords is mandatory. While this is addressed elsewhere I might suggest 
a language like:
   "When describing... a user <shall>..."
  The current phrase
    "To describe...  a user <shall> ..."
sounds to me (at least in isolation) like this is something a user has 
to do, as opposed to the required way of doing something if a user 
chooses to do it.

[I think this applies to some extent to other keywords in the standard too.]

     Tom

Tom McGlynn (NASA/GSFC Code 660.1) wrote:
> One question that I'd like to see clarified for these keyword is 
> whether if a have
>   TDMINx and TDMAXx
> that there is required to be an actual row I can point to which has 
> this value?
>
> Do we need to worry about round off errors between the binary and text 
> representation of numbers?
> E.g., suppose a number x is the minimum value in a table and
>    d.dddddddddddd
> is way that, e..g, Java, renders this value at full precision.
> I write
>     TDMINx = d.ddddddddd
> Have we violated the FITS standard if in infinite precision arithmetic 
> d.ddddddddd is actually > x.
>
> Alternatively do I have an error if I decide to address this issue but 
> subtracting a small delta from the minimum
> such that my actual the value I have in the TDMINx is a teeny bit less 
> than x.
>
> Not sure of how we address this precision issue but I think the 
> language currently is to restrictive.
>
>     Tom McGlynn
>
>
> Lucio Chiappetti wrote:
>> ANNOUNCEMENT:  START OF FORMAL PUBLIC COMMENT PERIOD
>>
>> This is to announce the official start of a 3-week formal Public Comment
>> Period on the incorporation of colum limit (aka TLMIN TLMAX) 
>> convention in
>> the FITS Standard.
>>
>> This is part of a process to incorporate the most useful, widely used
>> registered, and simple conventions (which are valid FITS constructs) 
>> into
>> the official definition of the standard.
>>
>> This convention defines the TLMINn/TLMAXn and TDMINn/TDMAXn keywords
>> describing the minimum and maximum values in table columns
>>
>> The proposed text consists just
>>
>> - in the ADDITION of a new section 4.4.2.7 (hilighted in violet colour)
>>    describing the four keywords
>>
>> - in the addition of CROSS REFERENCES to it in 7.2.2 and 7.3.2 (resp.
>>    for ASCII and binary tables)
>>
>>     and has been prepared by a technical team including L.Chiappetti,
>>     W.Pence, A.Dobrzycki, R.A.Shaw and W.Thompson (main editor
>>     W.Pence).
>>
>> - If the proposal is approved a section H.3 will be added to Appendix H
>>    describing the update, and the keywords will be listed in Appendix C
>>
>> The proposed draft text is available at
>> http://sax.iasf-milano.inaf.it/~lucio/FITS/Conventions/minmax-upd2.pdf
>>
>> Supporting material is provided in the FITS Convention Registry at the
>> following URL http://fits.gsfc.nasa.gov/registry/colminmax.html
>>
>> For general considerations on the Public Comment Period, the IAUFEC 
>> review
>> and background information on the FITS approval process please refer to
>> the announcement of Public Comment Period for CONTINUE issued earilier
>> today.
>>
>> Please review the text carefully and post any comments, criticisms, or
>> suggestions on the FITSBITS mailing list, separately for each 
>> convention.
>> ==================================================================
>>
>> The Public Comment Period starts today 19 June 2015 and will last 
>> formally
>> for 3 weeks until July 9 included.
>>
>
> _______________________________________________
> fitsbits mailing list
> fitsbits at listmgr.nrao.edu
> https://listmgr.nrao.edu/mailman/listinfo/fitsbits