change namespaceURI versioning policy

[pbiron]

WXR 1.0, 1.1 and 1.2 all use different namespaceURIs:

• http://wordpress.org/export/1.0/
• http://wordpress.org/export/1.1/
• http://wordpress.org/export/1.2/

respctively.

Doing namespace-aware parsing that is backwards compatible in the sense of handling WXR files from different versions with the same code would be MUCH easier if the WXR namespaceURI did NOT change with each version.

The namespaceURI in WXR 1.3-proposed is http://wordpress.org/export/ and would stay the same for any versions after that. The specific version of WXR in WXR 1.3-proposed (and any future version) is specified with rss/@wxr:version.

I recognize that this change would represent a MAJOR backwards imcompatibility (and thus will require A LOT of discussion and consensus building before it could be enacted) but it would would make FUTURE changes to WXR and the corresponding export/import code easier to deal with.

[pbiron]

Note that this is issue is not about the policy, to the extent there is one, for when to version WXR, itself. As best I can tell, the 1st and only mention of something that amounts to a policy on when to version WXR is in Trac ticket 5454: Additional metadata in wxr export format, which says, in part:

We should bump the version number iff there is a change that might affect backwards compatibility.