Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DataSetParameterHandle.java
* parameter. A parameter can also be input and output parameter. Each data set
 * parameter has the following properties:
 * 
 * <p>
 * <dl>
 * <dt><strong>Name </strong></dt>
 * <dd>a data set parameter has a required name.</dd>
 * 
 * <dt><strong>Position </strong></dt>
 * <dd>a data set parameter has an optional position for it.</dd>
 * 
 * <dt><strong>Data Type </strong></dt>
 * <dd>a data set parameter has a choice data type: any, integer, string, data
 * time, decimal, float, structure or table.</dd>
 * 
 * <dt><strong>Is optional </strong></dt>
 * <dd>whether this parameter is optional.</dd>
 * 
 * <dt><strong>Is Nullable </strong></dt>
 * <dd>whether the value of this parameter can be nullable.</dd>
 * 
 * <dt><strong>Is Input </strong></dt>
 * <dd>whether this parameter is an input parameter.</dd>
 * 
 * <dt><strong>Is Output </strong></dt>
 * <dd>whether this parameter is an output parameter.</dd>
 * </dl>
 * 
 */
public class DataSetParameterHandle extends StructureHandle