Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
implements
			IDesignElement,
			IPropertySet,
			IDesignElementModel
{
	/**
	 * The max length the display label for every element. If the length exceeds
	 * this limit, the exceeding part will be shown as "...".
	 */
	private static final int MAX_DISPLAY_LABEL_LEN = 30;
	/**
	 * Elements have an optional name. The name may be required by some element
	 * types. If so, the derived element class should enforce the use of the
	 * name. The name is non-localizable.
	 * <p>
	 * The name often occurs in a name space. Derived classes must enforce the