[isabelle-dev] Isabelle2013-2 release

Makarius makarius at sketis.net
Fri Nov 22 16:47:02 CET 2013

On Fri, 22 Nov 2013, Christian Sternagel wrote:

> honestly I do not remember why I dropped it, but I do remember that it 
> was no accident ... I guess I was convinced that it would not do any 
> harm

Just formally, the existing sources are always right.  This means when 
doing a change to override the status-quo, one needs to make a proof 
against it (mentally).  The result of the reasoning is then phrased in 
this typical changelog prose, to say in 2-3 words why something was done 
at that point of time.

This approach greatly helps in the software archeology process -- we have 
more than 20 years of recorded history already.  Actually, the Isabelle 
sources are much more youthful in that respect than many other projects of 
fewer years.


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