Name: zk Namespace URI: http://www.zkoss.org/2005/zk Namespace shortcut: zk JavaDoc: org.zkoss.zk.ui.metainfo.LanguageDefinition#ZK_NAMESPACE

It is the standard namespace for specifying ZK specific elements and attributes, such as the ZUML_Reference/ZUML/Elements/zk and ZUML_Reference/ZUML/Attributes/unless.

By default, ZK Loader will detect if an XML element or attribute is a special element or attribute and then handle it differently. However, if the default XML namespace is the ZUML_Reference/ZUML/Namespaces/Native or a component set that accepts any element name, such as ZUML_Reference/ZUML/Languages/XHTML, you have to specify the zk namespace. Otherwise, they will be interpreted as a component. For example,

<html xmlns="native" xmlns:u="zul" xmlns:zk="zk">
    <head>
        <title>ZHTML Demo</title>
    </head>
    <body>
        <script type="text/javascript">
        function woo() { //running at the browser
        }
        </script>
        <zk:zscript>
        void addItem() { //running at the server
        }
        </zk:zscript>
        <u:window title="HTML App">
            <input type="button" value="Add Item"
            onClick="woo()" zk:onClick="addItem()"/>
        </u:window>
    </body>
</html>