[Python-Dev] Re: [4suite] ReleaseNode interface in 4XSLT

[Mike Olson]

"Martin v. Loewis" wrote:
> 
> 
> In PyXML, I currently use
> 
> # Define ReleaseNode in a DOM-independent way
> import xml.dom.ext
> import xml.dom.minidom
> def _releasenode(n):
>     if isinstance(n, xml.dom.minidom.Node):
>         n.unlink()
>     else:
>         xml.dom.ext.ReleaseNode(n)
> 
> try:
>     from Ft.Lib import pDomlette
>     def ReleaseNode(n):
>         if isinstance(n, pDomlette.Node):
>             pDomlette.ReleaseNode(n)
>         else:
>             _releasenode(n)
>     _XsltElementBase = pDomlette.Element
> except ImportError:
>     ReleaseNode = _releasenode
>     from minisupport import _XsltElementBase
> 
> This code knows how to release minidom, 4DOM, and pDomlette nodes, and
> supports installations without 4Suite (i.e. without pDomlette). I've
> put this into xslt/__init__.py, so that all callers of
> Ft.Lib.pDomlette.ReleaseNode now need to call xml.xslt.ReleaseNode.
> If desired, I could produce a patch against the public Ft CVS.

What if we put these on the implementation, that or came up with a
standard interface on the node.  Then, every DOM imp that wants to be
compatible with xpath/xslt needs to support this interface?


node.ownerDocument.implementation.releaseNode(node)

or

node.py_unlink()




> 
> As a slightly independent question, such a function also ought to
> support DOM implementations not known to it; I'm thinking in
> particular of the Zope DOMs. I'd like to hear proposals on how such an
> interface should work; I see three options:

See above

> 
> a) it is an operation on the document node (or any node), as in minidom.
> b) it is an operation on the DOM implementation (almost as in 4Suite;
>    you'd need to navigate from the node to the implementation, then
>    you'd need a well-known operation on the implementation)
> c) the code assumes that no release activity is necessary for unknown
>    DOMs, effectively believing in reference counting, garbage collection,
>    acquisition, and other black art.

I like either a or b

Mike

> 
> Any comments appreciated, in particular
> 1. from the Ft maintainers on introducing xml.xslt.ReleaseNode, and
> 2. from authors of other DOMs on a general memory management API for
>    Python DOM.
> 
> Regards,
> Martin
> 
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-- 
Mike Olson				 Principal Consultant
mike.olson@fourthought.com               (303)583-9900 x 102
Fourthought, Inc.                         http://Fourthought.com 
Software-engineering, knowledge-management, XML, CORBA, Linux, Python