Sitemap Protocol

XML Sitemap Format: "The Sitemap Protocol allows you to inform search engine crawlers about URLs on your Web sites that are available for crawling. A Sitemap consists of a list of URLs and may also contain additional information about those URLs, such as when they were last modified, how frequently they change, etc.
Sitemaps are particularly beneficial when users can not reach all areas of a Web site through a browseable interface � i.e. users are unable to reach certain pages or regions of a site by following links. For example, any site where certain pages are only accessible via a search form would benefit from creating a Sitemap and submitting it to search engines."