You must have come across them. They are rather ubiquitous on the WWW and occur wherever there is a certain level of asynchronous communication with a server, a web browser and a neutral platform.
Rich internet applications have the sophisticated look and functions of desktop software, but the difference lies in the fact that they are honed to be operational on a web page. Their prominence has been triggered by web designers and even novice designers applying technologies like Flash and Ajax Frameworks.
The growth of the Internet as a medium of data and information exchange too has led to the emergence of RIAs in a major way. From all the applications and usability of RIAs they might very well be on their way to making the Internet a Web 3.0 experience.
Rich Internet applications are automatically updated, allowing clients the ability to process them. The comparatively high level of immunity to viral infection makes RIAs much better executables.
RIAs are not without drawbacks however. From an SEO point of view, the text featured in a rich Internet application might not be indexable by search engines. RIAs also need constant Internet connectivity. The screen readers face certain difficulty in detecting any dynamic changes in the HTML content.