[PPL-devel] Re: RFC: packaging the PPL for RedHat and Debian

[Roberto Bagnara]

Michael Tautschnig wrote:
>>>>
>>>> This package would have to depend on the availability of all 5 Prolog
>>>> systems and, in perspective also of OCaml, Java, Mathematica, ...
>>>> We need another idea.
>>>>
>>> Why does this interfaces-package depend on those systems - isn't it 
>>> the other way round (if one intends to use PPL)? But ...
>>
>>
>> You may need the language X development environment installed for
>> installing the X-PPL interface.  If you package the interfaces X-PPL,
>> Y-PPL and Z-PPL together you may end up with the situation where the
>> user is only interested in X-PPL but is required to have also Y
>> installed in order to install the single interfaces package.
>> This is something we want to avoid right from the start.
> 
> 
> I'm sorry, but I still don't get the point - why would I need the 
> "language X development environment" to install a library? IMHO
> 
> - it might be required to build it -> build-depend or
> - the library alone is of course not useful -> Suggests: ...
> 
> Would you mind giving an example - I just don't understand ...

It may be because byte-code needs to be regenerated by the exact
version of the environment that will be used by the user, it may
be because proper installation requires to detect some features
of the available development environment, it may be because an
index file to the available modules needs to be updated, it may
be because optional interfaces or their documentation are best
installed into a directory that only exists and is known if X
is already installed.  There are a number of possible
reasons.  In general, you cannot expect the installation procedure
of the development environment of language X to know about some
obscure X-PPL interface.  But the X-PPL can know about X
and may have to in case we want to simplify the user's life.
For example, we may decide to make the life of X-Prolog/PPL
users simpler by installing under /usr/local/lib/X/X-<version>/...
We can do so reliably only if X-Prolog version <version>
is already installed.  Remember that we often work with
software/languages that are no more than research prototypes:
we cannot expect they always do the right thing or provide
the same functionalities/flexibility one can find in more
professional software.
Cheers,

     Roberto

-- 
Prof. Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara at cs.unipr.it