XOM API for Processing XML with Java

[Elliotte Harold <elharo AT metalab.unc.edu>]

John Cowan wrote:

> There are three plausible implementation strategies: group the nodes
> before sending them to the XPath engine, group them on return from the
> engine, or insert and remove XPathText nodes behind the scenes from the
> tree itself during ordinary XOM operations, taking pains to hide them from
> the regular API.  The third trades off implementation pain for run-time
> efficiency, and IMHO isn't worth it.  I think the first strategy wins.

I think I'm following a variation of 1. The nodes are grouped before 
being passed to the XPath engine and ungrouped on return from it. It's 
all completely transparent to the public API. Clients never need to 
think about this. If I didn't ungroup what would come back would be 
something that was not in the original tree.

I think I see your point about wanting to know the boundaries of the 
XPath text nodes, even if they don't line up with XOM boundaries. (XOM 
should have a boundary wherever XPath does. It's just that XOM may have 
some extra boundaries as well.) I'm not sure I see the use case though. 
What sort of queries would make it useful to know the XPath boundaries?

> In any case, a ParentNode.normalizeTextNodes API should be provided,
> as it is useful outside XPath as well.

I've considered this at various times. It's not hard to write. So far I 
haven't been convinced it's a common enough need to be justified as part 
of the core API, especially since it's easy enough to write as a static 
utility method and such a method is already present in the samples 
package. I might be convinced otherwise if I saw the need to do this 
coming up frequently. However, the only time I've actually needed this 
is in XPath, and I've now got an alternative implementation that doesn't 
require that. A lot of the use cases for this I've seen in DOM are 
better addressed in XOM by the getValue() method.

--
Elliotte Rusty Harold  elharo AT metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
http://www.cafeconleche.org/books/xian3/
http://www.amazon.com/exec/obidos/ISBN=0596007647/cafeaulaitA/ref=nosim