ZUML (ZK User Interface Markup Language) is based on XML. Similar to HTML and XUL, it is used to describe UI in an easy-to-understand format.
In a ZUML document, each XML element instructs the ZK Loader which component to create. Each XML attribute describes what value to be assigned to the created component. Each XML processing instruction describes how to process the whole page, such as the page title. For example,
<?page title="Super Application"?> <window title="Super Hello" border="normal"> <button label="hi" onClick='alert("hi")'/>
where the first line specifies the page title, the second line creates a root component with title and border, and the third line creates a button with label and an event listener.