Re: Switching between DOM and SAX

Jonathan Robie (jonathan@texcel.no)
Sat, 19 Sep 1998 19:37:03 -0400


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