Wolfram Alpha (also styled WolframAlpha and Wolfram|Alpha) is a computational knowledge engine or answer engine developed by Wolfram Research. It is an online service that answers factual queries directly by computing the answer from externally sourced "curated data", rather than providing a list of documents or web pages that might contain the answer as a search engine might.
Wolfram Alpha, which was released on May 15, 2009, is based on Wolfram's earlier flagship product Mathematica, a computational platform or toolkit that encompasses computer algebra, symbolic and numerical computation, visualization, and statistics capabilities. Additional data is gathered from both academic and commercial websites such as the CIA's World Factbook, the United States Geological Survey, a Cornell University Library publication called All About Birds, Chambers Biographical Dictionary, Dow Jones, the Catalogue of Life, CrunchBase, Best Buy, the FAA and optionally a user's Facebook account.
Wolfram Alpha is written in 15 million lines of Mathematica code and runs on more than 10,000 CPUs. The database currently includes hundreds of datasets, such as "All Current and Historical Weather". The datasets have been accumulated over several years. The curated (as distinct from auto-generated) datasets are checked for quality either by a scientist or other expert in a relevant field, or someone acting in a clerical capacity who simply verifies that the datasets are "acceptable".
One example of a live dataset that Wolfram Alpha can use is the profile of a Facebook user. If the user authorizes Facebook to share his or her account details with the Wolfram site, Alpha can generate a "personal analytics" report containing the age distribution of friends, the frequency of words used in status updates and other detailed information. Within two weeks of launching the Facebook analytics service, 400,000 users had used it. Downloadable query results are behind a paywall but summaries are accessible to free accounts.