Remove Bill/Vendor

[Derek Atkins]

True, and most of the code does this (including the business
features).  However I think Bill was requesting an ability to
undo _AFTER_ commit.  And _that_ isn't really possible.

-derek

linas at linas.org (Linas Vepstas) writes:

> On Tue, Mar 25, 2003 at 04:01:13PM -0500, Derek Atkins was heard to remark:
> > I'm not sure what you mean by "general purpose undo".  There is not
> > a centralized place where all objects are added/removed..  So there
> > is no way (short of rototilling a lot of code) to re-architect the
> > system to allow this.
> 
> Derek,
> 
> Please excuse the following, cause I know yo know it already, but your remarks
> scared me  ...
> 
> One of many reasons for having begin/end constructs around data is to
> be able to mark up atomic, undo-able data chunks.  In principle,  If 
> you surrounded your data correctly with being/end in the right places 
> (this also requires your data design to be 'normal' or 'orthogonal'),
> then undo is 'easy'.   You implement undo by using begin/end to make a 
> copy of the old data.  At 'end', you string this copy onto your necklace 
> of saved undo thingies.  Implementing undo is then a matter of pulling
> pearls off the necklace.
> 
> Easier said-than-done.  One important issue is that the data really be 
> normal, so that you only need to save a copy of the atomic data chunk, 
> instead of saving the entire state of the whole damn system.   Clearly,
> if saving the state of the whole system was needed for undo, then indeed 
> undo would be untenable.
> 
> --linas
> 
> 
> -- 
> pub  1024D/01045933 2001-02-01 Linas Vepstas (Labas!) <linas at linas.org>
> PGP Key fingerprint = 8305 2521 6000 0B5E 8984  3F54 64A9 9A82 0104 5933

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available