(XML)shearing files between programs without data loss

[Leigh Dodds]

> Several users have reported problems of data loss when passing files
> between programs. With XML and the Document Object Model, this will
> never happen, because it's easy for a programmer to work on the document
> tree, just adding nodes where additions have been made by user, and
> leaving the other parts unchanged. So a round-trip beetwen programs will
> be feasible, leading to a composite document having a common core of
> elements understood by both programs, some elements understood by
> program A only, and some by program B only.

Indeed, so long as the subset of elements shared by the two applications
are handled correctly in both cases. Application A may decide to
encode a date as simply year-month-day. Application B may decide
to encode it as year-month-day-time. Load file from Application B into
Application A and unless you're careful you may lose precision.

Also consider the following:

   <character number="8">
      <description>outer edge of front wing</description>
      <comment>shape</comment>
      <multi type="unordered">
         <state number="1">convex</state>
         <state number="2">straight</state>
         <state number="3">concave</state>
         <state number="4">irregular</state>
      </multi>
   </character>

   <application-B-tag references="8">
      I referred to standard chart X to finally decide on shapes.
   </application-B-tag>

Application A, ignoring the application B specific tag, on request
of the user deletes character 8. Now load the file up into
application B and you've got a problem - you've lost the character
being referenced.

XML does not solve these problems. Although it brings us closer
to a toolkit that does. Data modelling and agreeing on standard
(extension formats) will help to solve these problems.

See http://www.bath.ac.uk/~ccslrd/delta/#adv, particularly
"xml is not a magic bullet" and the references to postings
on the XML-DEV mailing list.

Sorry to pick holes, but I'd hate for XML to be oversold to the
participants on this list. Its important to see beyond the
hype.

Cheers,

L.