[AstroPy] POLL: vision for a common Astronomy package

Mark Sienkiewicz sienkiew at stsci.edu
Tue Jul 5 13:45:27 EDT 2011

Brian Kloppenborg wrote:
> I am, however, a little concerned that the current vision statement 
> seems to exclude the use of existing officially sanctioned (i.e. by the 
> IAU) routines that are written in other languages.

I don't see that the vision statement excludes this case.  I only see 
where it says that these other routines will not be REQUIRED in order 
for Astropy to work at all.

Are you proposing that I must install the SOFA software before I can 
install Astropy?  Are you proposing that I must agree to the SOFA terms 
of use (which are more restrictive than GPL or BSD licensing) before I 
can use Astropy?  If this is the case, a user might be reluctant even to 
try Astropy because of the complications involved.  I can tell you from 
first hand experience that I have decide not to even evaluate A LOT of 
free software projects because of excessive number/difficulty of 

If not, are you proposing that Astropy contain a package that can make 
use of pysofa for optional features?  That is, Astropy can work without 
pysofa, but may be able to do more things if pysofa is present?  I think 
this case is explicitly called out in the vision statement. 

If you look in the current astrolib.pywcs, you'll see that it makes use 
of a wcs library by incorporating the entire source code of the third 
party library.  This is particularly convenient for users because they 
can just install the python package and expect it to work.  This is a 
way that you can make third party routines available without creating 
additional dependencies, though it does involve some work for the 
developer.  (But then, that is what developers do, right?  They do some 
extra work to make things easier for the user.)

So, I don't think that the kind of thing you are looking for is 
explicitly excluded, but there are some complications involved.


p.s.  Specifically for SOFA, you might want some way for a python 
program to tell you whether it used any part of SOFA during this run, 
and is therefore affected by the SOFA license requirements.

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