Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Siri, the voice-controlled personal assistant is able to interpret natural-language commands and respond, providing information. Siri was originally developed by a research lab called SRI International, it originated as a part of the project CALO (Cognitive Assistant that Learns and Organizes). After Apple's acquisition of Siri, it gained a worldwide popularity and was relaunched as a built-in feature of iPhone 4S. Learn more about Apple's personal assistant as well as its authors and developers in this book.