Version information: this feature is available since release 4.1.

OpenWebCMS? contains an agent named (wCrawlerSitemapXML). It produces a XML sitemap of all content with the property 'for search engines'. You can use it to submit the sitemap to the Google Webmaster Tools.

For that I suggest to create an URL redirection in your Domino configuration as follows:

Incoming URL pattern: /sitemap.xml
Redirect to URL: /<path to your cms database>/(wCrawlerSitemapXML)