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
* <code>SemanticExcpetion</code>.
	 * 
	 * @return the validation error list.
	 */
	public List getErrors( )
	{
		if ( errors == null )
			return new ArrayList( );
		return errors;
	}
	/**
	 * Returns the identifier for locating element to user. This identifier
	 * string helps user locate this element in user interface. If this element
	 * has name defined, the name and element type are returned with the form
	 * "ElementType('Name')". Otherwise, locate the first container with name
	 * and generate the containment path with the form,
	 * "Container.Slot[Position]". If no container has name defined, "report" or
	 * container element type will be used as container's identifier, depending
	 * on whether this element is added into one report design.
	 * <p>
	 * For example,
	 * <ul>
	 * <li>report.body[0] - The first element in body slot
	 * <li>table("myTable") - The table named myTable
	 * <li>table("myTable").detail[0].cells[3] - The forth cell of the first
	 * row in table
	 * </ul>
	 * <p>
	 * Note: the localized name is used for element type and slot name.
	 *