As of JSP 2.0, a JSP container must support a jsp:id attribute to provide higher quality validation errors. The container will track the JSP pages as passed to the container, and will assign to each element a unique "id", which is passed as the value of the jsp:id attribute. Each XML element in the XML view available will be extended with this attribute. The TagLibraryValidator can then use the attribute in one or more ValidationMessage objects. The container then, in turn, can use these values to provide more precise information on the location of an error.

The actual prefix of the id attribute may or may not be jsp but it will always map to the namespace http://java.sun.com/JSP/Page. A TagLibraryValidator implementation must rely on the uri, not the prefix, of the id attribute.