Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In (multithreaded) object-oriented programming, asynchronous method invocation (AMI), also known as asynchronous method calls or asynchronous pattern is a design pattern for asynchronous invocation of potentially long-running methods of an object. It is equivalent to the IOU pattern described in 1996 by Allan Vermeulen. The event-based asynchronous pattern in .NET Framework and the java.util.concurrent.FutureTask class in Java use events to solve the same problem. This pattern is a variant of AMI whose implementation carries more overhead, but it is useful for objects representing software components. In most programming languages a called method is executed synchronously, i.e. in the thread of execution from which it is invoked. If the method needs a long time to completion, e.g. because it is loading data over the internet, the calling thread is blocked until the method has finished. When this is not desired, it is possible to start a "worker thread" and invoke the method from there.