Since we are investigating storage formats for PythonCard, I went ahead and
asked the question about the data format stability of ZODB. The question and
response are below.

ka

-----Original Message-----
From: Barry A. Warsaw [mailto:barry@[...].com]
Sent: Wednesday, January 30, 2002 8:14 AM
To: Kevin Altis
Subject: Re: FW: zodb data format stability

> >>>> "KA" == Kevin Altis <altis@[...].com> writes:

    KA>  Unless you know the answer, one of the questions I want to ask
    KA>  about ZODB, which probably applies to any object data store is
    KA>  the long-term stability of the format.

    KA>  I'm mostly concerned about things like creating say an
    KA>  addresses database with Python 2.1 and ZODB and then of course
    KA>  being able to pass that database around to a Mac, Linux,
    KA>  Windows and have it work. But then there is the issue of
    KA>  switching versions of Python and/or the ZODB module say a
    KA>  couple of years from now, opening the database and having it
    KA>  get corrupted, even though no changes were made to your
    KA>  program or framework. Also, do we need to be careful to use
    KA>  built-in Python types such as int and string? Do you know what
    KA>  I mean re my concerns?

ZODB is pretty closely tied to Python pickles, which are guaranteed to
be portable across platforms and Python releases.  They are
endian-safe and 32/64-bit safe, so you should have no problem moving
Data.fs files between different systems.

Pickles are a Python-specific data format so if you wanted to
interchange the data between different programming languages, you'd
need to use an intermediate format.

The data format for FileStorage is well defined so even if we changed
the Data.fs format in a later version of ZODB (unlikely), we'll no
doubt provide migration/update tools.  Backwards compatibility is very
important to us.

Hope that helps,
-Barry


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