Bug 145991 [Regression]Invalid data set should not be allowed to drag or "Insert in layout"
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DataSetHandle.java
* <li>Filters.
 * <li>Computed columns. Sorting, grouping, aggregations and similar transforms
 * are defined by the report elements that use the data set.
 * </ul>
 * <p>
 * The application can use scripts to execute code on certain data set events.
 * <p>
 * To get a handle for the data source, uses the following example:
 * 
 * <pre>
 *    
 *        
 *    		DataSetHandle dataHandle = designHandle
 *            findDataSet( &quot;My First Data Set &quot; );
 *     
 * </pre>
 * 
 * <p>
 * This class works with the static design definition of the data set. Many
 * clients will prefer to work with the TBD class that provides both the static
 * definition and additional design information retrieved from the data
 * provider. For example, a particular data set may not define a result set in
 * the design file if the data provider can provide the result set definition
 * itself. This handle will return null for the result set handle. However, the
 * TBD class will provide the full result set: either by returning the one in
 * the design file, or by obtaining it from the data provider.
 * 
 * @see org.eclipse.birt.report.model.elements.SimpleDataSet
 */
public abstract class DataSetHandle extends ReportElementHandle