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Two postinsts that generate the same file - who owns it?

Hi all,

With Javi and Francisco García, I am trying to hash out an RFC for
astronomy programs in Debian (spacechart, starplot, kstars, etc.) and
how they should use star data that may be available (currently packaged
are gliese and yale, both in non-free).  We have come upon the problem
detailed below.

Some astronomy programs require that the star data be converted from
"raw" flat ASCII form to their own format, because it's (a) easier for
the program to interpret, (b) in binary form and thus smaller and faster
to use, or some other reason.  For instance, there is the "starconvert"
script in the starplot package, gliese2spacechart.pl will be in the next
release of spacechart, etc.

Any program that can use one of these data files after some
preprocessing should find their own preprocessed version of the data
available when both the program and the data package are installed.  Our
solution is to generate the preprocessed version of the data file in
both of the following cases:

1) in the postinst of the data package, but only when the program is

2) in the postinst of the program package, but only when the data
package is installed.

(This is done both on install and on upgrade, since an upgrade to the
program package may have changed the required data format, and an
upgrade to the data package may have introduced new data.  Think of it
like "update-mozilla-chrome" that all the mozilla related packages call.)

The main questions: Since it is not possible to determine which postinst
has generated the preprocessed data file, who "owns" it?  That is, when
should it be uninstalled: When either of {program package, data package}
are removed?  Only when the data package is removed?  Only when _both_
are removed?  Should it stay on the system forever [I hope not!]?

As a side question, where should the preprocessed data go --
/usr/share/<program-package>/ or /var/lib/<program-package>?

Thanks in advance for your input.

Kevin B. McCarty <kmccarty@princeton.edu>   Physics Department
WWW: http://www.princeton.edu/~kmccarty/    Princeton University
GPG: public key ID 4F83C751                 Princeton, NJ 08544

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