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Parsed Representation of an XML

• To: xml-dev@l...
• Subject: Parsed Representation of an XML
• From: "Ram Menon" <menon_dev@h...>
• Date: Wed, 05 May 2004 13:37:08 +0530
• Bcc:

Hi All,

  At a high level, XML Processing could involve the following steps.
   1) Read the XML file
   2) Parse the XML to an in-memory representation
   3) Use the Parsed Representation to extract values, format values through 
XSLT, etc, and so on.

What I wanted to know is the fact as to why do not have a parsed 
representation based on the access pattern and usage of the parsed document 
?
For e.g. the XSLT might use the document to retrieve three values from one 
particular subtree, or maybe process all the children at a particular depth 
within a subtree.

WHy not have another input to the parser, which is, an abstract 
representation of the access pattern, and then the in-memory document be 
optimized for that particular pattern? [i.e optimal in terms of the access 
time and memory usage].

i.e.
XML file + Access-Metadata -------**XML Parser** -->Optimal Internal 
Representation

The DOM internal representation fundamentally is a single instance of a 
particular nature of "Packing" of the XML. This form of "Packing" may not be 
beneficial for certain use-cases. Why not think out of the box and come up 
with some different sort of packing that allows all the required nodes to be 
"close" to each other, to facilitate fast traversal, and maybe lower memory 
usage by the fact the parsing only generates a partial document which is 
just what might be required.
For e.g. one particular sdenario might be the "inversal" of the XML 
structure, as such; [I am just choosing this ad-hoc];i.e. the "supposed to 
be" leaf nodes of the parsed tree appear as the top level elements within 
the parsed representation, and each of them have a reference [in the form of 
some attribute or something on those lines] to their parents along with 
them; very similar to viewing a n-ary tree reversed. Another form of packing 
could be a "cube" like packing, where we build a "multi-dimensional data 
structure" based on the structure of the XML content. The cube can be 
accessed from all six of its faces, which might correspond to the 
principally accessed members within the document. All these are a subset of 
the possible structures that could be generated as a result of parsing the 
XML. Each of these structures have definitive traversal patterns and costs.

This might seem a very vague idea, but would be good if somebody can build 
on it for better.


rgds,
Ram Menon

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