gzipped images in SIAP 1.0

[Roy Williams]

Dear DAL people

I am soliciting comments on compliance to the ancient SIAP 1.0 protocol 
[1], in a place where it seems a bit fuzzy.

I would like to know if it is possible for a compliant SIAP to return 
*compressed* FITS images. I note that some so-called SIAP services have 
already been built where the image access URL (the so-called acref) ends 
in .fits.gz, and so I expect that these are gzipped fits images. 
However, the standard seems to say that this is non-compliant[2].

I am asking because I am writing client code, and I want *only* fits 
files, no jpegs or anything like that. Currently it just checks for a 
format of "image/fits" and rejects anything else. Is this too harsh?

-- If somehow the answer is yes, that gzipped images *can* be returned
    by a SIAP, can somebody recommend a MIME type to use? 
    Would it be application/x-gzip?
-- Does the client need to parse the URL? (i.e. look for ending in
    .fits.gz or .fit.gz or .FITS.gz or all the other combinations)
-- Does anyone remeber the intention of the comma-delimited list of MIME 
types?     Should  my code look for "application/x-gzip,image/fits"
    Or maybe the other way around?
-- Are there any other MIME types out there that my code should check for?

Thank you
Roy Williams

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[1] http://www.ivoa.net/Documents/WD/SIA/sia-20040524.html

[2] Image Format.  The service MUST support a parameter with the name 
FORMAT to indicate the desired format or formats of the images 
referenced by the output table. The value is a comma-delimited list 
where each element can be any recognized MIME-type. Typically, these 
will be of the major type "image"; however, "text/html" can be specified 
to request URLs for HTML documents describing and/or previewing the image.