xml-dev - Re: Switching between DOM and SAX

[Jonathan Robie <jonathan@texcel.no>]

At 02:20 PM 9/19/98 -0400, John Cowan wrote:
 
>> When processing large documents building entire trees is
>> resource intensive and time consuming. Sometimes you only
>> the power of tree navigation stuff for sub-parts of the
>> source document.
>
>This is difficult with the DOM, because every Node must have
>a pointer to the root (Document) Node.

Lazy evaluation is perfectly OK in the DOM, which says absolutely nothing
about the physical representation of a Node, e.g. it does not say that a
Node must have a pointer, merely that it be able to return a reference to
the root. Every Node must be capable of returning such a pointer when
asked, but until someone asks for the root node, there is no need to
construct such a node. Similarly, a Node must be able to return references
to parent or child nodes, but those nodes need not be constructed until the
reference is asked for.

Jonathan
 
jonathan@texcel.no
Texcel Research
http://www.texcel.no

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