xml-dev - Re: XML tools and big documents (was: Re: Is there a size limitation on

[David Megginson <david@megginson.com>]

Ingo Macherius writes:

 > > The problem comes if the parser tries to build a tree rather than
 > > simply reporting an event stream.
 > 
 > How many real world applications will be happy with just the event 
 > stream ? XSL-visualization always needs two trees, the parser tree 
 > and the resulting Formatting Object Tree (FOT). Double impact ! XML-
 > querys/DOM need to build a transformed versions. Triple impact !

Yes, but often the trees can be built and discarded at a fairly low
level.  For example, if I have a serialised database table like

  <table>
   <entry>
    <name>David Megginson</name>
    <email>david@megginson.com</email>
   </entry>
   <entry>
    <name>Ingo Macherius</name>
    <email>macherius@darmstadt.gmd.de</email>
   </entry>
   <!-- etc., 2,500,000 times -->
  </table>

I do not need to build a tree for the whole document; instead, I can
cache the information for each entry (or each n entries, for
efficiency), dump it into my SQL database (or whatever), then move on
to the next set.

The second situation is where you are using XML to serialise a data
model that is already well-defined (as for vector graphics).  In this
case, it makes more sense to build the specialised object tree
directly from the event stream rather than building a DOM tree only to
tear it down.  Specialised object trees can be considerably smaller
than a corresponding DOM tree, depending on the format.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@ic.ac.uk
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/
To (un)subscribe, mailto:majordomo@ic.ac.uk the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo@ic.ac.uk the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa@ic.ac.uk)