The ZK framework has a rich set of components, a mark-up language, powerful development tools, and great documentation, along with being open source and an event-driven Ajax framework.

It is composed of an Ajax-based, event-driven engine, a rich set of XHTML and XUL components, and a mark-up language called ZUML, which is used for creating feature-rich user interfaces.

Is developed by Microsoft to assist development environment that contains event-driven programming language.