XOM API for Processing XML with Java

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

Wolfgang Hoschek wrote:

> How about decoupling the exclusive Canonicalizer CVS from the XPath impl 
> by having

I haven't written the exclusive canonicalizer yet. Do you mean the 
document subset canonicalizer?

> public final void write(Nodes nodes)

It's possible, and indeed I originally planned to do it that way. 
However, there are some tricky bits:

1. The Nodes argument can't contain nodes from multiple documents.
2. The canonicalizer would have to sort the Nodes into document order 
(doable)
3. The canonicalizer would have to remove duplicates from the Nodes. 
(doable)
4, I don't think the Nodes could be disconnected from a Document. I'm 
not sure about this. Perhaps they could.

The real issue is that document subset canonicalization is defined in 
terms of an XPath expression selecting a list of nodes from a document. 
It is not defined in terms of an arbitrary list of nodes. I'm worried 
that  there might be unexpected side effects if I attempt to 
canonicalize just anything.

Then again I can see good reasons to want to do this. Possibly I could 
provide both options, but we'd need to consider what would happen with 
arbitrary Nodes objects first.

I also wonder if maybe passing a Nodes object should have different 
semantics than passing in a document and an XPath expression that 
selects those nodes. For instance, you might want to fully canonicalize 
each node and all its descendants, attributes, and namespaces rather 
than just the start-tags and end-tags you'd get with an XPath expression 
that only selected those elements.

--
Elliotte Rusty Harold  elharo AT metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
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