Rich Internet Applications (RIAs) are web applications that have functionality similar to desktop applications. They transfer user interface processing to the web client but keep data on the application server. RIAs can be responsive, interactive with rich user interfaces, support real-time communications, and have broad reach. They are becoming the face of Service-Oriented Architectures (SOAs) by exposing well-defined services that applications can access. RIAs also enable Software as a Service (SaaS) models by providing interfaces for things like reservations, dispatching, billing, and flight tracking systems. Popular technologies for building RIAs include Adobe Flex, Java Applets, OpenLaszlo, Microsoft WPF, and Ajax.