[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: using namespaces to version
It is essential to separate the concept of namespaces from the concept of schemas - they are not the same. Currently, UK Government namespaces are not versioned. Schemas carry a major version number in the URI and instance documents contain the full version number. The logic is that, as others have said, the namespace just makes the tag names unique, so does not need to change. It is the schema that affects validation. Schema changes that result in an upwardly compatible schema (e.g. no new mandatory elements, no elements removed) have the minor version changed, so the URI remains the same. Changes that result in the schema not being upwardly compatible have the major version number (and hence the URI) changed. 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. Paul Spencer CTO, alphaXML Ltd alphaXML is recruiting XML Consultants +44 (0)1491 630053 http://www.alphaxml.com -----Original Message----- From: Tony Coates [mailto:Tony.Coates@r...] Sent: 03 May 2001 10:19 To: xml-dev@l... Subject: Re: using namespaces to version On 02/05/2001 23:29:50 Warren Hedley wrote: >I'm wondering if anyone on the list has any strong opinions about >the use of namespaces for versioning. In particular, am I likely >to run into any problems if I base my namespaces on the Dublin Core >format shown below? I have a strong opinion that namespace URIs should be explicitly versioned. I'm not against also having the version in an attribute value on the top-level element, but I see that as a complement, not a replacement. The problem with "canonical namespace URIs" that point to the most recent version of a spec is that existing applications don't automatically rewrite themselves to fit the new version of the spec. An application needs to be able to detect quickly whether a document uses a version of a schema that it can deal with. If not, it then needs to reject it, or pass it on to a different application, or get it converted to a version that it can deal with. It is (needlessly) harder to get this to work properly if the one namespace URI applies to all versions of a schema.
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