Re: using namespaces to version

[Jonathan Borden <jborden@mediaone.net>]

Paul Spencer wrote:
>
> But now RDDL comes along and gives us something for the namespace to point
> to. This could result in a need to version namespaces so that we can point
> to different RDDL documents. But if we do this, what happens (as David
> Carlisle mentioned) to processing code that uses fully-qualified names
(such
> as code that uses XPath expressions)? I'm just starting to think about
this
> for UK Govt.
>

I think the reasons whether or not to change a namespace URI (i.e. create a
new namespace) when new versions of something come out have been well
addressed. Generally I agree that changes in a namespace vocabulary which
_are not_ backward compatible should be accompanied by a new namespace,
whereas version changes that _are_ backward compatible should use the same
namespace (in order to allow software to continue to recognize the
documents). These are all important design decisions.

RDDL does provide a mechanism to tie versioning of namespace related
schemata to the namespace. One can embed multiple rddl:resources with
natures and purposes that indicate prior versions of the same type of
resource (e.g. XML Schema).

Similarly a RDDL resource might indicate a related namespace URI, perhaps
nature="http://www.rddl.org/" and
purpose="http://www.rddl.org/purposes#prior-version" would indicate a prior
version of a RDDL document/namespace URI , whereas the purpose
http://www.rddl.org/purposes#prior-version with a nature
http://www.w3.org/2001/XMLSchema would indicate a prior version of an XML
Schema in the same namespace.

Does this make sense?

-Jonathan