Processing Instructions
From Documentation
Directive
Each XML processing instruction specifies how to process the XML document. It is called directives in ZK. For example, the following directive specifies the page title and style.
<?page title="Grey background" style="background: grey"?>
Notice that there should be no whitespace between the question mark and the processing instruction's name (i.e., page in the above example).
You can also use EL in instructions like:
<?page automaticTimeout="true" title="${personalTitle}"?>
<?component name="loc-datebox" extends="datebox" locale="${somelocale}"?>