[Zope] Zope Database in XML

[Jim Fulton]

A side project of mine is to allow conversion to and from
Zope databases (and export files) and XML.  This will allow
people to more easily access their data without Zope and correct
problems, such as moved or renamed software modules, that prevent
data from being unpicklable.

I've completed a first cut at a tool for converting a Zope 
database to XML format. It is provided in the file 'bbb.py'
in a 'utilities' directory that will be included in the 
distribution directory of the next Zope release.

If you want to get this now, you can get it via Zope
public CVS access.  See 
http://www.zope.org/Community/Services/CVS_public_access
for details.

To run the tool, use:

  python utilities/bbb.py -rxml var/Data.bbb

For now, the tool provides a way to "get at"
your data without Zope and get a bit more of an idea
of how Zope organizes data in the database.

The file uses a module 'ppml.py' (Python
pickle markup language :) that must by in the
same directory as bbb.py or in the Python path.
ppml.py provides for conversion from Python pickles
to XML.  It will eventually provide conversion
from XML to Python pickles.  Comments from members
of the XML SIG (those who happen to spend time here
too) would be welcome.  I haven't written a formal DTD
for this XML format.  I would like to use a standard Python
XML pickle format, but I'm not sure if such a thing exists 
yet.

I took the approach of conversion to and from Python pickle
format for two reasons:

  - It allows me to do conversion to and from
    database format without actually creating any 
    (application objects).  This is much faster than
    creating actual objects and does not require that
    any application Python modules needed to unpickle 
    objects be around or working.  For example, this allows
    conversion of objects that are not unpicklable.

  - It means that many of the implementation details
    of pickling can be avoided.

Of course, in combination with the Python pickle modules, 
pickling objects to XML is straightforward:

  import pickle, ppml
  print ppml.ToXMLloads(pickle.dumps(myobject))

Enjoy.

Jim

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