Quoting Jasen Betts on Sun 5 Jan 2003 22:16 to Jan Vermeulen:

 jb> 04-Jan-03  Jan Vermeulen wrote to Scott Little

 JV>> How can you be 100% sure that you will get the old data back when
 JV>> generaing an SLF list from the XML data

 jb> Is it desirable to get 100% the same data back anyway?

    It is a must.

 jb> things like the ordering of the flags or the method used to publish
 jb> internet address aren't critical and some systems work better with
 jb> one form and others with a different form.

    If you're not strict to start with, you create a nursery for bugs.

 mb>>> Of cource we have to see to it that everything we change also can
 mb>>> be provided in a backward compatible format for the sysops.

 JV>> Ok, the intention is there. But how sure can you be that not even
 JV>> one byte will get lost or damaged in the operation

 jb> One way is to prove the software and specification mathematically,
 jb> but first a design is needed.

    Ok.

 JV>>>> How can you be 100% sure that you will get the old data back
 JV>>>> when generaing an SLF list from the XML data?

 sl>>> You can't, but that's dependant on the broken-ness of the input
 sl>>> SLF.  Theoretically, the SLF -> XML conversion will only extract
 sl>>> "known good" data, leaving the rest as
undecipherable nonsense
 sl>>> which XML native programs will ignore, but will be restored when
 sl>>> converted back to SLF.

 JV>> This implies that an XML list generated from the nodelist at one
 JV>> place will not yield the same nodelist somewhere else. I don't
 JV>> like that

 jb> why?  as long as it contains the apropriate information does it
 jb> matter,

    Do not start to get lax even before you got the specs. You're sure not
to succeed if you do.

 jb> when the extractor has to produce SLF for that nodeline it cant
 jb> know how the line was originallt organised, but it can express the
 jb> information in a sensible way.

 jb> suppose this goes in:

 jb> ,100,213.84.184.65,Wormerveer,Jan
 jb> _Vermeulen,31-75-6400418,9600,CM,XA,V32B
 jb>    ,V42B,V34,VFC,V120L,V120H,X75,IBN,PING,U,ENC

 jb> if it comes out like this:

 jb> ,100,213.84.184.65,Wormerveer,Jan
 jb> _Vermeulen,31-75-6400418,9600,XA,V32B,
 jb>    V34,V42B,VFC,V120L,V120H,X75,IBN,PING,CM,U,ENC

 jb> does it really matter?

    Not in this particular, well chosen example. But surprises tend to
happen just when you think you got everything under control.


    -==-