Wolfram Alpha (also styled WolframAlpha and WolframAlpha) is an answer engine developed by Wolfram Research. It is an online service that answers factual queries directly by computing the answer from structured data, rather than providing a list of documents or web pages that might contain the answer as a search engine might.^{[1]}
Wolfram Alpha is based on the computational platform Mathematica, written by British scientist Stephen Wolfram in 1988.^{[2]} Wolfram Alpha was announced in March 2009 and subsequently released on 15 May 2009.^{[3]}
Overview
Users submit queries and computation requests via a text field. WolframAlpha then computes answers and relevant visualizations from a knowledge base of curated, structured data. Alpha thus differs from semantic search engines, which index a large number of answers and then try to match the question to one.
WolframAlpha is built on Wolfram's earlier flagship product, Mathematica, which encompasses computer algebra, symbolic and numerical computation, visualization, and statistics capabilities. The answer usually presents a humanreadable solution. Wolfram has said of the engine:
"All one needs to be able to do is to take questions people ask in natural language, and represent them in a precise form that fits into the computations one can do,"^{[2]}
WolframAlpha is capable of responding to particularly phrased naturallanguage factbased questions such as "Where was Mary Robinson born?" or more complex questions such as "How old was Queen Elizabeth II in 1974?" It displays its "Input interpretation" of such a question, using standardized phrases, e.g. "Mary Robinson  place of birth" or "age  of Queen Elizabeth II (royalty)  in 1974". (The answer for Robinson includes "Ballina, Mayo, Ireland", a variety of contextual information regarding Ballina, County Mayo, and a link to an online biography of Robinson. The answer for Elizabeth is "Age at start of 1974: 47 years", and a biography link.)
It is also capable of performing calculations on data using more than one source:
WolframAlpha makes inferences from a smaller set of core information. In this way it has many parallels with Cyc, a project aimed at developing a commonsense inference engine.
Wolfram Alpha doesn't answer queries which require a narrative response as "What is the difference between the Julian and the Gregorian calendars?" but will answer factual or computational questions such as "1 June in Julian calendar".
Licensing partners
Wolfram Alpha is used to power some searches in the Microsoft Bing and DuckDuckGo search engines.^{[4]}^{[5]} It is also queried by Apple's Siri for factual question answering as well as the Dexetra's clone of it for Android Iris.
Technology
WolframAlpha is written in 15 million lines of Mathematica^{[6]} (using webMathematica and gridMathematica) code and runs on 10,000 CPUs (though the number was upgraded for the launch).^{[7]}^{[8]}
 Example: "lim(x>0) x/sin x" yields the expected result, 1, as well as a possible derivation using L'H pital's rule, a plot, and the series expansion.
The database currently includes hundreds of datasets, such as "All Current and Historical Weather". The datasets have been accumulated over approximately two years, and will continue to grow. The range of questions that can be answered will grow with the expansion of the datasets.^{[9]}
History
Launch preparations began on 15 May 2009 at 7 pm CDT (16 May 2009 0:00 UTC) and were broadcast live on Justin.tv. The plan was to publicly launch the service a few hours later, with expected issues due to extreme load. The service was officially launched on 18 May 2009.^{[10]}
Wolfram Alpha has received mixed reviews.^{[11]}^{[12]} Wolfram Alpha advocates point to its potential, some even stating that how it determines results is more important than current usefulness.^{[11]}
On Dec 3, 2009, an iPhone app was introduced. Some users^{[13]} considered the initial $50 price of the iOS app unnecessarily high since the same features could be freely accessed by using a web browser instead. They also complained about the simultaneous removal of the mobile formatting option for the site.^{[14]} Wolfram responded by lowering the price to $2, offering a refund to existing customers^{[15]} and reinstating the mobile site.
Wolfram Alpha Pro
On February 8, 2012, WolframAlpha Pro was released,^{[16]} offering users additional features for a monthly subscription fee. A key feature is the ability to upload many common file types and data including raw tabular data, images, audio, XML, and dozens of specialized scientific, medical, and mathematical formats for automatic analysis. Other features include an extended keyboard, interactivity with CDF, data downloads, and the ability to customize and save graphical and tabular results.^{[17]}
Along with new premium features, Wolfram Alpha Pro has led to some changes in the free version of the site:
 An increase in advertisements on the free site.
 Text and PDF export options now require the user to set up a free account.
 The option to request extra time for a long calculation used to be free but is now only available to subscribers.
Criticism
InfoWorld has published an article^{[19]} warning readers of the potential implications of giving an automated website proprietary rights to the data it generates but Richard Stallman disagrees that such rights are transfered.^{[20]}
References
Further reading

Wolfram Alpha: A New Way To Search?, Stephen Wildstrom, BusinessWeek, 9 March.

Stephen Wolfram's Answer To Google: If Wolfram/Alpha works as advertised, it will be able to do something Google can't: provide answers that don't already exist in indexed documents. by Thomas Claburn, InformationWeek, 10 March 2009.

Better Search Doesn t Mean Beating Google by Saul Hansell, The New York Times, 9 March 2009.

Wolfram Alpha will Take Your Questions Any Questions, Ian Paul, PC World, 9 Mar 2009.

Wolfram Alpha: Searching for Truth: Stephen Wolfram talks with Rudy Rucker about his Upcoming Release by Rudy Rucker, H+ Magazine.

"A hungry little number cruncher: Wolfram Alpha search tool mines databases to yield mathbased replies" by Hiawatha Bray, The Boston Globe, 5 May 2009
External links
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