xml-dev - Re: Common XML (was Re: Document Feature Requirements)

["Simon St.Laurent" <simonstl@simonstl.com>]

At 08:23 PM 4/10/00 -0400, David Megginson wrote:
>"Don Park" <donpark@docuverse.com> writes:
>
>> I would agree with you if it was just the parser and the application
>> with nothing in between.  Unfortunately, most e-commerce systems is
>> based on N-tier designs with lots of middleware and mediums between
>> the data source and the application.  You have to worry, not just
>> about the size of the your toilet hole, but all the pipes between
>> your home and the sewer plant.  Sorry about my rather yucky
>> analogy. <g>
>
>Most e-commerce players are going to use XML only for interchange;
>despite the best efforts of self-proclaimed XML vendors, few real
>players would be foolish enough to redesign all of their internal
>around XML.

I think you missed something here.  N-Tier doesn't mean redesigning
internal systems around XML - it just means that multiple layers of
processing are taking place.  Those could be SAX filters, those could be
systems on different machines.  Assuming that a PI or comment that entered
at the start is going to survive the transfer, even if no explicit
transformations take place, is basically foolhardy.

We aren't writing the rules, merely pointing out the potholes.  

Element structures are more robust than PIs and comments.  Should that
surprise anyone?  

For all the reasons stated here about why PIs and comments aren't element
structures, no.

If robustness matters, if the content inside those PIs and comments needs
to be able to survive trips through multiple tiers of processing, then
consider alternatives - like clearly labelled element structures.  If it
doesn't, then use PIs and comments.

[Side note: XSLT's defaults for PIs and comments, to me, say a lot
indirectly about the 'robustness' of PIs and comments, especially in
contrast to the rules for elements: The built-in template rule for
processing instructions and comments is to do nothing.  <xsl:template
match="processing-instruction()|comment()"/>]

Simon St.Laurent
XML Elements of Style / XML: A Primer, 2nd Ed.
Building XML Applications
Inside XML DTDs: Scientific and Technical
Cookies / Sharing Bandwidth
http://www.simonstl.com

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