Re: [xsl] XPath over DOM

Subject: Re: [xsl] XPath over DOM
From: Uche Ogbuji <uche.ogbuji@xxxxxxxxxxxxxxx>
Date: Thu, 15 Feb 2001 22:19:42 -0700
> > > Are there any Java-based XSLT or XPath implementations (at
> > least partial
> > > functionality) that can traverse over existent DOM object,
> > as opposed to
> > > creating their own in-memory structure? I need to be able
> > to provide my own
> > > Document object built by my own parser, not just DOM APIs
> > over internal
> > > processor structure (as Saxon implementation).
> >
> I think Xalan and Oracle can both do this.
> > Why would any Java XSLT processor have a problem working with
> > another's DOM nodes?
> Saxon doesn't do it (at present) because of the cost and complexity of (a)
> sorting nodes into document order when they don't contain a serial number,

I see the cost, but this should not exced cost of conversion.  In abstract 
terms, it's a single tree traversal, with one assignment per node.  Is there 
really any property of Java that would make this more expansive than a tree 
traversal with complete object instantiation and initialization per node?

> (b) skipping over and counting nodes correctly in the presence of things
> such as entity reference nodes, CDATA nodes, and unnormalized text nodes,
> and

There is a normalize() if the user doesn't mind mutation.  The rest, at least 
as I've attacked it, is a matter of wrapping, again in the same pass as 
doc-order indexing.

> (c) dealing with the multitude of ways that the DOM allows namespace
> nodes to be (or not be) represented.

???  Do you mean Level 1 vs. Level 2?

Uche Ogbuji                               Principal Consultant
uche.ogbuji@xxxxxxxxxxxxxxx               +1 303 583 9900 x 101
Fourthought, Inc.                
4735 East Walnut St, Ste. C, Boulder, CO 80301-2537, USA
Software-engineering, knowledge-management, XML, CORBA, Linux, Python

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