Yesterday Google demonstrated experimental search extensions that utilize semantic information contained in Gmail messages about things like Amazon purchases and airline flights, extending their earlier work on semantic search.
Semantic information enables Google to provide better search results and answer specific questions. For example, as shown here, Google "knows" the values of some of George Washington's attributes, including the fact that Mount Vernon was his home.
It also knows some of the values of some of Mount Vernon's attributes:
Google will test the use of semantic information in Gmail messages in a trial limited to 1 million volunteers. (You can sign up here).
If you sign up, Google will use information about your airline flights and Amazon purchases that it finds in Gmail messages. For example, it will use the values of the attributes of airline flights like airline, departure and destination airport, and flight date to find things like your "flight to Cancun last year."
Google's strategy is to improve search a little bit at a time -- baby steps.