Re: [xml-dev] The purpose of a namespace URI is ...

[Dan Vint <dvint@dvint.com>]

Coming from the SGML world, I prefer to think of them as a Public 
Identifier in a different format. I process documents and I don't 
typically use JAVA or other programming language to deal with them. 
As such, I prefer to have a unique identifier for versions changes. 
If not for minor changes, anything that introduces a change that 
would break backward compatibility should be identified.

..dan

At 12:04 PM 12/1/2012, Timothy W. Cook wrote:

>An interesting conversation indeed.  My understanding was namespaces were
>to be used as specific pointers.
>
>As an example; I have a project at 
><http://www.mlhim.org>www.mlhim.org using this as the base I
>add xmlns and then the version of the schema to create the complete
>namespace for each schema.
>
>Examples:
>xmlns:mlhim2="<http://www.mlhim.org/xmlns/mlhim2/2_3_0>http://www.mlhim.org/xmlns/mlhim2/2_3_0";
>xmlns:mlhim2="<http://www.mlhim.org/xmlns/mlhim2/2_4_0>http://www.mlhim.org/xmlns/mlhim2/2_4_0";
>xmlns:mlhim2="<http://www.mlhim.org/xmlns/mlhim2/2_4_1>http://www.mlhim.org/xmlns/mlhim2/2_4_1";
>
>[actually 2.4.1 will be released this coming week]
>
>are all three active versions of this reference model schema.  Though they
>are essentially the same schema. Small changes to improve usability  etc.
>were made in each version. There are constraint schemas developed against
>them and they will always exist as they were initially created,
>representing healthcare concepts.  Once there are constraint schemas
>(Concept Constraint Definitions or CCDs) built against them and there is
>instance data against those CCDs.  They must remain there forever in order
>to provide the syntax and semantics for the instance data, where ever that
>instance data exists.
>
>I cannot decide from the conversation if this is considered best practice
>or not.  I had at one time thought to use xmlns:mlhim2="
><http://www.mlhim.org/xmlns/mlhim2>http://www.mlhim.org/xmlns/mlhim2"; 
>in parallel with the versioned ones
>above but that is not functional as far as I can tell since the CCD needs
>to always know where the reference model schema it was built against
>exists.
>
>Thoughts?
>
>Thanks,
>Tim
>
>
>On Sat, Dec 1, 2012 at 4:44 PM, Fraser Goffin 
><<mailto:goffinf@gmail.com>goffinf@gmail.com> wrote:
>David you may very well be right, but on a practical level, it is more
>likely that due to a change in pure *syntax*, for example wanting an
>existing complexType to have a new mandatory element, a change of the
>namespace may be necessary to clearly signal that break. I'm not
>saying that's right, I'm just saying that whilst a new namespace may
>at one level create a new language, if it substantially inherits it's
>semantics from the previous version but because of a practical issue
>can't really maintain the same namespace ....
>
>That's why I said earlier that a data model can be 'damaged' because
>of the 'leakage' of shortcomings of the language used to express it.
>Whilst we could philosophically satisfy ourselves that if implementers
>followed a particular approach to processing messages using that
>language the problem wouldn't exist, again, reality would suggest that
>many (perhaps most) don't do that and instead rely on features of 'off
>the shelf' processors to do most of the heavy lifting but still
>exhibit the processing flaw (e.g. strict XSD validation rather than
>'selective/elective').
>
>It's a conumdrum.
>
>Fraser.
>
>
>On 01/12/2012, David Carlisle 
><<mailto:davidc@nag.co.uk>davidc@nag.co.uk> wrote:
> > On 30/11/2012 20:22, Fraser Goffin wrote:
> >> But isn't it usually the case that you would only change the
> >> namespace for a MAJOR version change, and it is this explicit and
> >> deliberate breaking change that you are signalling by doing so (ie. a
> >> significant change of semantics and sometimes syntax).
> >
> > Well stronger than that, If you change the namespace you have changed
> > the name of every token in the language so it's not a new version it's a
> > new language. Sometimes that's what you want to do SGML->XML dsssl to
> > xslt etc but if the language is plausibly a new _version_ of an existing
> > language it ought to have the same namespace (a policy that isn't always
> > followed:-)
> >
> > David
> >
> >
> >
>
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