Re: [office] Concerning backwards compatibility in odf 1.2

[robert_weir@us.ibm.com]

Hi Dave,

I must admit that I was not considering
the idea of time travel, but it is a thought. 

In general I'm not too far off from
what you are stating.  We don't want to be trapped by earlier versions
of the format, and be unable to solve real problems by the necessity of
perpetuating old mistakes.  Other companies with other legacy formats
have that problem, and it is no end of trouble for them.

But I think we also need to consider
that we're giving out three ODF versions within a year, which is a pretty
good pace.  There needs to be some semblance of stability, and the
ability for the user to have reasonable expectations of forwards and backwards
compatibility in such a short time frame.  One way we can help set
these expectations is by adopting a clear TC on what type of compatibility
guarantee we're making with any new version of the standard.  This
may not be the same guarantee with every update.  Maybe we track that
with major and minor version numbers, and we make one set of guarantees
with minor version updates, and few or no guarantees with major number
updates.  ODF 1.2 is feeling to be like a major version update.  I
sometimes wonder if it should be called ODF 2.0.

-Rob


"Dave Pawson" <dave.pawson@gmail.com>
wrote on 03/29/2007 03:04:49 PM:

> On 29/03/07, robert_weir@us.ibm.com <robert_weir@us.ibm.com>
wrote:
> >
> > Hi Lars,
> >
> > You right to draw a distinction between application compatibility
versus
> > document compatibility.
> >
> > The four basic questions I have in mind are:
> >
> >    1. Are documents that are conformant according to
the ODF 1.0 or ODF 1.1
> > specifications also conformant according to the ODF 1.2 specification?
 If
> > not, what are the exceptions?
> 
> That (for forwards compatibility) I can rely on the 'lars' updater
software
> to get there? Not yours, but someone with motivation enough to get
me
> from version n to n+1.
> <goal>The files on disk can live for 5 years</goal>
> 
> 
> 
> 
> >
> > I'd like to hope that the list of exceptions is small.  Whenever
possible we
> > should try to introduce compatible changes.
> 
> But only as a 'nice to have'?
> 
> >
> >    2. Are documents that are conformant to the ODF
1.2 specification also
> > conformant to the ODF 1.0 or ODF 1.1 specifications?   If
not, what are the
> > exceptions?
> 
> None. you want to go back in time?
> Your problem.
> Don't expect OSS to support you?
> A bit crude, but I don't see us (or anyone with sense) supporting
the future?
> 
> 
> 
> >
> > This will be less likely to be true.  Whenever we add a
new mandatory
> > element or attribute, or expand the allowed range of attribute
values, we
> > are losing this level of compatibility.
> 
> The gain is that the new item is a step forward?
> 
> 
> >
> >    3. Can an application that is written to the ODF
1.2 specification able
> > to also load ODF 1.0 and ODF 1.1 documents?  If not, what
are the
> > exceptions?
> 
> The hard parts.
> Error: Some parts of this document are not compatible with version
(n-1)
> please update your application.
> 
> That sounds quite reasonable to me?
> 
> 
> >
> > In other words, if someone sits down next year with the ODF 1.2
standard,
> > and writes an application using just the info in that specification,
will
> > their code be able to also read legacy ODF documents?  I'd
like to be able
> > to preserve this.  So we should not remove anything from
the ODF
> > specification.
> Only with 'pre-processing'?
>   Please don't constrain ODF to handling n year old instances?
> I'm sure company X will have motivation to provide an 'update' app/filter.
> Hopefully they will share it and ease the pain of others.
> Don't hold the standard back for laggards :-)
> 
> 
>  We can deprecate and provide alternatives.  But we probably
> > should try to keep the ODF specification in a comprehensive state,so
it has
> > all information needed to implement the current, and previous
versions of
> > ODF.
> 
> I'd like to restrict that to version (current) - 1?
> 
> 
> 
> 
> >
> >    4. Can an application that is written to the ODF
1.0 specification also
> > load ODF 1.2 documents?  If not, what are the exceptions?
> I don't care. Go update your application.
> Please feel free to blow up on 'future' data.
> 
> 
> 
> >
> > This is a question about degrading gracefully.  This will
not work in the
> > general case.
> The case should be (IMHO). Blow up, with a gentle error message,
> "I've met something I don't understand.
> The file is from version x.y, I don't process that"
> 
> IMVHO, that is 'degrading gracefully'.
> 
> 
> 
> > So I'd emphasize the documentation aspect of this.  We can
break backwards
> > compatibility where necessary, but we should carefully document
each
> > instances where we do this, as an aid to implementors.
> 
> Or restrict it?
> 
> Just my 2 penneth.... sorry, 2 euro's.
> 
> regards
> 
> -- 
> Dave Pawson
> XSLT XSL-FO FAQ.
> http://www.dpawson.co.uk