XML for distributed processing

[David Megginson]

El Melody Chile writes:

 >  Bosak says (in his paper "XML, Java, and the future of the Web")
 > that "its utility ultimately lies in the fact that a
 > computation-intensive process, that would otherwise entail an
 > enormous, extended resource hit on the server has been changed into
 > a brief interaction with the server followed by an extended
 > interaction with the user's own Web client".  I can't see how this
 > is directly due to XML, would the same process not be possible
 > using a Java applet and data written in *any* industry-specific
 > representation language?  Is there any specific benefit associated
 > with using XML to implement this language?

One advantage is the fact that XML has a concept of both physical
(entity) and logical (element) structure.  You can put together a
document from many different sources anywhere on the Internet (or any
other network), and produce an entirely different logical structure
for use by your application.  For example, here's a document that gets
its first chapter from a hypothetical server in Canada, its second,
from a server at an American university, and the second paragraph of
its third chapter, from a server in Finland (of course, if you're
using a Java applet, your web browser must allow applets to make
TCP/IP connections to multiple hosts):

  <?xml version="1.0" standalone="no"?>
  <!DOCTYPE book SYSTEM "book.dtd" [
    <!ENTITY chap01 SYSTEM
      "http://xmlserver.nowhere.ca/cgi-bin/get-chap?id=1">
    <!ENTITY chap02 SYSTEM
      "ftp://cow.college.edu/pub/chapters/chapter-02.xml">
    <!ENTITY para01 SYSTEM
      "http://santas.village.fi/text/english/somepara.xml">
  ]>
  <book>
  <title>My Book</title>

  <!-- first chapter -->
  &chap01;

  <!-- second chapter -->
  &chap02;

  <!-- third chapter -->
  <chapter>
  <title>This is the third chapter</title>

  <para>First paragraph.</para>

  &para01;

  <para>Third paragraph.</para>

  </chapter>

  </book>

Another advantage is the fact that many people are using it.  You
could invent a different syntax that did the same thing, but why
bother, especially when there's already lots of free and commercial
software supporting XML.

A final advantage is that XML is not language-, software-, or
vendor-specific; instead, it's based on an International Standard, ISO
8879, that has been in widespread enterprise use for over a decade.


All the best,


David

-- 
David Megginson                 ak117 at freenet.carleton.ca
Microstar Software Ltd.         dmeggins at microstar.com
      http://home.sprynet.com/sprynet/dmeggins/

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