Re: [office] Concerning backwards compatibility in odf 1.2

[robert_weir@us.ibm.com]

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?

I'd like to hope that the list of exceptions
is small.  Whenever possible we should try to introduce compatible
changes.

   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?

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.


   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?

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.  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.

   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?

This is a question about degrading gracefully.
 This will not work in the general case.  For example, an ODF
1.2 document would be using the standard ODF 1.2 OpenFormula spreadsheet
formulas.  But no ODF 1.0 editor understands these.

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.  

-Rob

Lars.Oppermann@Sun.COM wrote on 03/28/2007 04:56:41
AM:

> Dear TC,
> 
> We concluded in our last conference call, that many of the problems
that 
> we are seeing with the debate about lists and numbered paragraphs
> circles around the various notions about the guarantees that we are
> willing to make concerning the behavior of applications that were
> implemented with ODF 1.0/1.1 in mind when they are to open an ODF
1.2 
> document.
> 
> There has also been the question of ODF 1.1 in ODF 1.2 applications,
> which I do not view as a problem at all. An ODF 1.2 Application can
tell 
> an ODF 1.1 document from an ODF 1.2 document by looking at the (now
> required) version-attribute in the office:document element. The 
> application can then act accordingly. In cases, where implementors
have 
> come up with different interpretations of the ODF 1.1 spec, the 
> application can chose to come up with its own interpretation or ask
the 
> user - that is not of concern to this group. (There also is a 
> meta:generator element that implementors may use in this scenario.)
> 
> With regards to ODF 1.2 documents in ODF 1.1 applications, it is in
my 
> opinion useful to look at two cases:
> (a) Documents including new elements/attributes not present in 1.1
> (b) Documents constrained to the 1.1 vocabulary
> 
> In the case of (a), I do not want to guarantee that an old application
> will display the document like a 1.2-aware application. This is both
> unrealistic an infeasible. We should do our best to design new features
> in a way that allows old applications to "gracefully degrade",
rather 
> than completely breaking access to the document.
> 
> The case of (b) is largely unproblematic, except for situations, in
> which different ODF 1.1 applications implement certain aspects of
the 
> specification in a different way - whether this is due to ambiguities
in 
> the specifications of implementation errors is not relevant. We as
a TC 
> cannot change these old applications, and an interoperability 
> disagreement among two 1.1 applications cannot be addressed by anything
> that we specify for ODF 1.2.
> 
> The lists and numbered-paragraph proposals that have been created
by 
> openoffice.org and koffice developers are very much in-line with the
> view presented above. They strike a balance between providing a good
> design for our new specification. ODF 1.2 applications will not have
> much burden when importing old documents and ODF 1.1 applications
will 
> be able to display documents in a gracefully-degrading manner. If
none 
> of the new constructs are used, the old applications will behave as
> always. If the new constructs are used, they will be ignored, yielding
a 
> presentation, that is degraded when comparing to the presentation
> offered by a newer 1.2-compliant application. This can from my point
of 
> view be accepted.
> 
> I would welcome if TC members would indicate whether their view 
> regarding these matters is in line with what was presented above so
that 
> we may use the resulting guidelines to come to a conclusion regarding
> the ongoing debate about lists and numbered-paragraphs - hopefully
being 
> able to vote on a proposal in the next call.
> 
> Bests,
> Lars
> -- 
> Lars Oppermann <lars.oppermann@sun.com>      
        Sun Microsystems
> Software Engineer              
                     
    Nagelsweg 55
> Phone: +49 40 23646 959            
            20097 Hamburg, Germany
> Fax:   +49 40 23646 550            
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