The first was Mathematica—the system in which all of Wolfram|Alpha is implemented. Mathematica has three crucial roles in Wolfram|Alpha. First, its very general symbolic language provides the framework in which all the diverse knowledge of Wolfram|Alpha is represented and all its capabilities are implemented.
Second, Mathematica's vast web of built-in algorithms provides the computational foundation that makes it even conceivably practical to implement the methods and models of so many fields. And finally, the strength of Mathematica as a software engineering and deployment platform makes it possible to take the technical achievements of Wolfram|Alpha and deliver them broadly and robustly.