RE: [xml-dev] Caution using XML Schema backward- or forward-compatibilit

["Costello, Roger L." <costello@mitre.org>]

Thanks David.

Here is a question for the community:

"My XML Schema is backward-compatible."  What does that statement mean
to you?  

Does it mean:

A) The new XML Schema can validate old instance documents.  [XML Schema
backward-compatibility only guarantees syntactic -- validation --
compatibility with old instance documents]

B) The new XML Schema can validate old instance documents, the
semantics of new data are compatible with old data, and the
relationships (e.g. co-constraints) of new data are compatible with old
data.  [XML Schema backward-compatibility guarantees syntactic --
validation -- compatibility, semantic-compatibility, and
relationship-compatibility with old instance documents]

C) Other (please specify)


/Roger

 

-----Original Message-----
From: David Carver [mailto:d_a_carver@yahoo.com] 
Sent: Wednesday, December 26, 2007 3:39 PM
To: Costello, Roger L.
Cc: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Caution using XML Schema backward- or
forward-compatibility as a versioning strategy for data exchange

I agree, but I always include in any definition that semantic 
interoperability must be maintained as well. So even though the schema 
may still validate the data, it has to pass further compliance 
constraints outside of the validation. I would also add that Schematron

will run into the same issue as well..particularly if the meaning of 
elements and attributes change.

> Accordingly, I am raising caution to the common fallacy: "If my XML
> Schema is backward-compatible then my application can process old
> instance documents."
>
> Do you agree?
>