Google has introduced its long awaited blog search service, becoming the first major search engine to offer full-blown blog and feed search capabilities. Blog Search is Google's search technology focused on blogs. Google is a strong believer in the self-publishing phenomenon represented by blogging, and Blog Search will help users to explore the blogging universe more effectively, and perhaps inspire many to join the revolution themselves.

Google web search allows you to limit results to popular blog file types such as RSS and XML in web search results for some time, and its news search includes some blogs as sources, Google hasn't had a specialized tool to surface purely blog postings. In fact, while all of the major search engines have been dabbling with blog and feed search, none has done much with blog search until now.

Google's new service (in beta, naturally) is available both at http://www.google.com/blogsearch, The Blogger Dashboard ,The Navbar on any BlogSpot blog and http://search.blogger.com. Google blog search scans content posted to blogs and feeds in virtually real-time .Blog Search enables you to find out what people are saying on any subject of your choice.

Google defines blogs as sites that use RSS and other structured feeds and update content on a regular basis. Although Google Blog search focuses primarily on content published to the blogosphere, it's not a true full-text search across all sources. This is because some publishers only syndicate excerpts of content via RSS. Google's blog search indexes all of the content it finds in feeds, but does not attempt to access and index the full content available on a publisher's web server.

Blog Search indexes blogs by their site feeds, which will be checked frequently for new content. This means that Blog Search results for a given blog will update with new content much faster than standard web searches. Also, because of the structured data within site feeds, it is possible to find precise posts and date ranges with much greater accuracy. Blog Search can also be used to find either specific posts or entire blogs. The main search results always return links to posts. However, when there are entire blogs that seem to be a good match for your query, these will appear in a short list just above the main search results.

Google does use information garnered from its crawl of the web to identify potential blog sources, looking at meta data, links and other clues that might point to a feed. However, Google also respects the robots.txt protocol, and will not crawl any content that's disallowed by a publisher.

Google blog search results point primarily to individual blog postings, with a title and snippet from each-strongly resembling Google's web search results. In some cases, links to "related blogs" are presented at the top of search results if a query suggests that the user is looking for a particular blog rather than a specific blog posting.

Results are sorted by date, with recent posts appearing at the top of the list. You can also choose to sort results by relevance. Blog search uses its own unique approach to relevance ranking, it also draws a lot from Google's web search ranking algorithms. Google blog search has an advanced search page and a number of commands are available. allowing you to limit searches by title, author and date or date range. You can also limit results to a specific language, or apply the Safe Search filter to results.

You can also discover who's linking to a post or blog using the link:command. Unlike Google web search, which sharply curtails the number of results displayed using link: command to discourage abuse by search marketers, the link: command in blog search displays a comprehensive and nearly complete list of sources linking to a particular post or blog.

Google Blog Search is available in English as well as Brazilian Portuguese, Dutch, French, German, Italian, Korean, Russian, and Spanish. One can restrict results to any of 35 specific languages by using the Advanced Search options. Just check the boxes next to the languages you want to include. By default, results include blogs written in all languages.