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
* <dt><strong>By name </strong></dt>
 * <dd>Elements can have a name. Names are unique within a name space. However,
 * many elements are anonymous. Names are required only when the element will be
 * referenced. Some elements, such as styles, data sources, and data sets, exist
 * to be referenced and so require a name. Most other elements are seldom
 * referenced, and so the name is optional.</dd>
 * 
 * <dd><strong>By navigation </strong></dt>
 * <dd>Elements can be found via navigation. One can start at the module and
 * work down though the containment hierarchy. Every valid element can be
 * reached via navigation. Indeed, the definition of element creation, from the
 * perspective of the design, is when the element is added to the containment
 * hierarchy. Similarly, the definition of deletion, again from the perspective
 * of the design, is when the element is dropped from the containment hierarchy.
 * </dd>
 * 
 * <dd><strong>By pointer </strong></dt>
 * <dd>The design tool itself references elements mostly using Java pointers.
 * That is, once the application finds an element of interest, it simply holds
 * onto it using a pointer.</dd>
 * 
 * <dd><strong>By ID </strong></dt>
 * <dd>The web designer needs a simple way to reference items across calls to
 * the server. None of the above is both simple and consistent. Element IDs
 * provide this service. IDs are valid only within a single design "session". A
 * session is the time between when a design is loaded into memory, and the time
 * that the design is released. IDs are <em>not </em> valid across sessions,
 * and are not persistent. The application must enable IDs by calling
 * {@link org.eclipse.birt.report.model.metadata.MetaDataDictionary#enableElementID}.
 * Call {@link #getID}to get the ID of an element. Call