[isabelle-dev] Isabelle preferences

[Makarius]

On Fri, 29 Oct 2010, Makarius wrote:

> Right now I do not fully understand the existing preference system -- I 
> need to look at it again when it is officially integrated into 
> Isabelle/Scala -- so it is hard to say what is the simplest possible 
> flexible solution.  Maybe time in seconds, but as a float, but this is 
> apt to cause confusion with persistent preferences of users out there.

There is a depper problem behind this: in the past few years we have 
accumulated quite a few "settings" or "preferences" for PG that are 
essential for certain system components, and end up somewhere in global
configuration files in the user's home, without any indication of the 
Isabelle version.

This makes it hard to change the meaning of settings at a later stage, 
without causing strange problems.  I have already had reports by users 
that configured ATPs manually according to old instructions by Larry, 
which caused a breakdown of Sledgehammer in Isabelle2009.  The solution 
was to ask users to purge old preferences manually.


For official releases, we have already 
$ISABELLE_HOME_USER/heaps/Isabelle2009-2 with explicit version prefix. 
One could apply this principle to the whole $ISABELLE_HOME_USER content, 
i.e. always work via ~/.isabelle/Isabelle2009-2 for example.  (I have seen 
this scheme Netbeans, and variations for Mozilla.)

This would solve the problem for official releases, but users might have 
to copy old stuff manually.  It also does not address the needs of people 
that are hooked on "the latest snapshot", or "unidentified repository 
version" as it is called officially.


Any further, better, ideas?


 	Makarius