What is a ZUL file?
ZUL File Format
ZUL files are XML-based, consisting of different elements to construct user interface. The ZK loader uses each XML element to create a component. The overall processing of the page elements such as page title, description, etc. are described by each XML processing instruction of ZUML.
In the following example of ZUML code, 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.
<?page title="Super Application"?> <window title="Super Hello" border="normal"> <button label="hi" onClick='alert("hi")'/>
The ZUL schema can be downloaded from http://www.zkoss.org/2005/zul/zul.xsd.