Bug 449954

Thanks for report, discussed in the past in #234345. I would say triggerin would
be good solution (or at least change to Requires(post): openjade)

*** This bug has been marked as a duplicate of 234345 ***

Requires(post) doesn't help as it still gets pulled in for it.  A trigger might,
but triggers are very tricky to get right.  

A simple fix might be checking if the openjade catalog is there and registering
with it if so, else just leaving it for the openjade %post to later pick up

As I maintain both packages, I will think about that solution - although I would
say trigger in docbook-dtds is slightly better (as the goal is to register
openjade catalogs in docbook-dtds catalogs - and it has almost nothing to do
with openjade package). 

So we have three ways now:
1) Keep it as it is - will save no space on LiveCD
2) triggerin openjade in docbook-dtds - will save space on LiveCD (as openjade
catalogs will be not registered when no openjade available), a bit tricky to
have it running correctly, but it is not affecting other packages
3) move registration to openjade - will save space on LiveCD - but could cause
troubles in some situation (e.g. if you install openjade first, it will not be
registered in docbook-dtds - which could cause some troubles). So registration
has to be doubled (done in both - openjade and docbook-dtds %post - just for
cases that the second package is already installed - that's almost as tricky as
the trigger solution and affects both packages as they have to be synchronized.

I like the trigger solution, as this affects only one package and will have
minimal impact if properly written. But as you said, it could easily be broken
and has to be tested before applying to Fedora (definitely not to F9 or lower to
not break stable release).