Add versioning to an xml sitemap?

[ATT_SEO]

Is there a way to add versioning to an xml sitemap? Something like <version>x.x</version> outside of the <urlset>?</urlset>

I've looked at a bunch of sitemaps for various sites and don't see anyone adding versioning information, but it seems like it would be a common issue - I can't believe someone hasn't come up with some way to do it.

[Martijn_Scheijbeler]

I'm mostly curious why you would want to do this and if so, why not do this on the back-end of the generation of your sitemaps instead of in the sitemaps itself?

[ATT_SEO]

Huge corporation with lots of sites and large number of people on disparate teams (marketing, technical, management) involved in maintaining/updating the sites -- easier for anyone to be able to take a quick look at the sitemap online to see what version it is.