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
public final boolean isVirtualElement( )
	{
		return baseId != NO_BASE_ID;
	}
	/**
	 * Copied the structure from the parent element to the element itself. Local
	 * properties of the contents will all be cleared.Please note that the
	 * containment relationship is kept while property values of the content
	 * elements are not copied.
	 * 
	 * @param module
	 *            the module
	 * 
	 * @return <code>true</code> if the refresh action is successful.
	 *         <code>false</code> othersize.
	 * 
	 */
	public boolean refreshStructureFromParent( Module module )
	{
		DesignElement parent = getExtendsElement( );
		if ( parent == null )
			return false;
		
		return ElementStructureUtil.updateStructureFromParent( this, parent );
	}
	/**
	 * Resolve and returns the virtual parent element. If the element is not
	 * virtual element, <code>null</code> will be returned. Otherwise, find
	 * and returns the virtual parent using the <code>baseId</code>.
	 *