> Remember that little incident in 2000 when the London 
> millennium bridge was
> closed immediately after opening due to excessive wobbling when people
> walked across it? I can't guarantee that my recollection is 
> accurate, but
> I'm sure they were trying to put this down to that software classic, a
> 'Design feature'.

The Millenium Bridge wobble is indeed instructive.  Engineering is usually a 
profession that is conservative and places great emphasis on codifying and 
learning from past mistakes.  Much bridge design work uses well-established, 
trustworthy principles.  The Millenium Bridge designers deliberately pushed the 
boundaries to produce something novel and exciting.  Never before had a 
suspension bridge had the suspension and decking in the same plane (i.e. the 
deck doesn't "hang" from the suspension, its balanced on/between the 
suspension).  The result was strong enough but had unexpected dynamics i.e. it 
I am confident that this experience is already in the text books, standard data 
tables and CAD tools.  The engineering body of knowledge had been added to and 
the problem should not recur.

This is where the software community can learn:

1.  We are appalling at learning from previous mistakes (other than in 
perfecting our ability to repeat them!)
2.  We routinely push the boundaries of what we try and achieve by leaping 
instead of stepping.
3.  We routinely adopt novel and untried technology in preference to proven and 
trustworthy alternatives.  Indeed, mature technology often seems to be rejected 
precisely because it is not new, novel or exciting enough.

The Millenium Bridge made news precisely because such engineering faiures are 
rare; software engineering failures make the news because they are so common 
the papers would be empty if they weren't reported! 




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