This is to announce my latest released extension, Data Transfer. You can see the extension page here:
This extension displays XML for pages in a set of categories and/or namespaces that the user specifies; the XML is created by turning the template calls and template fields within the page into XML fields; any text outside of template calls gets placed in one or more "free text" fields. It also supports two slightly different formats for the XML, though the difference is mostly aesthetic. Though this extension doesn't rely on SMW, it was created with sites that use semantic templates in mind, as another way for such sites to emulate more conventional relational-database-driven sites. You can see it in action on Discourse DB:
Though it looks like I've recently been creating extensions at a manic pace, this extension was actually mostly developed in August and September of last year, inspired by a conversation I had with someone who was trying to exchange data between a semantic wiki and some other applications, and I've been using it for one of my projects for a while now; I just never got around to polishing it up and releasing it until now.
A planned addition to this extension (though who knows when it will be added) is to also allow for the importing of XML, using the same data format. The extension could also be upgraded to support other data formats, like CSV; that's why the extension has a generic name, as opposed to something like "View XML".
Semantic MediaWiki, of course, has its own mechanism for exporting and importing data, using RDF/OWL. I see the RDF export and the XML export as having different and complementary uses: the former is extremely flexible, and allows for widespread usage of one's data, while the latter is a much simpler format, and allows for small-scale, proprietary, site-specific usage.