Google on Wednesday began allowing users to extend online searches to include messages stored in accounts at Web-based email service Gmail.

"Sometimes the best answer to your question isn't available on the public Web -- it may be contained elsewhere, such as in your email," Google search senior vice president Amit Singhal said in a blog post.

"We think you shouldn't have to be your own mini search engine to find the most useful information; it should just work."

Google invited people to visit google.com/experimental/gmailfieldtrial to sign up to take part in the new feature, which was still taking shape.

"We're developing a way to find this information for you that's useful and unobtrusive, and we'd love your feedback," Singhal said.

The trial was limited to English language searches and messages in Gmail accounts.

Enhancements under development include a feature for organizing air travel confirmation emails so that a query of "my flights" would serve up results that include a concise list of bookings.

"These are baby steps, but important ones on our way to building the search engine of the future," Singhal said.

Those steps include upgrading Google search to look beyond query words to figure out what people are actually seeking online.

"Knowledge Graph" technology built to recognize people, places or things signified by keywords was extended beyond the United States to every English-speaking country in the world on Wednesday, according to Google.

"The Knowledge Graph is built to understand real things in the world," Google fellow Ben Gomes told AFP when the improvement debuted in May.

Gomes envisions Google search being able to eventually answer tricky questions such as where to attend an outdoor Lady Gaga concert in warm weather or the location of an amusement park near a vegetarian restaurant.

For now, users of Google search in English will start seeing boxes on search pages suggesting what they are interested in finding.

A demonstration showed that searching for the word "Rio,", for example, prompted the search engine to point out that one is likely interested in a Brazilian city, Las Vegas casino, or film.

Google has refined its algorithm to comb information from databases such as Freebase and Wikipedia to give context to words and then use general search patterns when it comes to what people tend to want, Gomes said.

Google has also added a serendipity factor by surfacing potentially surprising facts.

For example, a search on "Simpsons" cartoon creator Matt Groening resulted in a Knowledge Graph box that noted his parents and sister have the same first names as his well-know fictional characters -- Homer, Marge and Lisa.

Google's Knowledge Graph has been programmed to recognize more than 500 million people, places, or things using a combined total of about 3.5 billion attributes and associations between bits of information.

The change was expected to affect a large number of queries, and was tailored with mobile gadgets in mind since it lets people dive deeper into searches with taps of touchscreens.

Google is under constant pressure to refine its service to defend its place as the world's favorite search engine, and the wealth of online advertising revenue that comes with that dominance.