Bug 120291 Data source and data set extended from library in a report are invalid.
Description: Data source and data set extended from library in a report are invalid. Steps to reproduce: 1. Drag a data source and data set from library explorer view. Noticed that their names are different from the names in library. 2. I want to use the data source extended from library to create a new data set. The data source is invalid. 3. The data set from library is also invalid. When editing it, NullPointerException is thrown out.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/StructureFactory.java
/**
	 * Creates an empty data set cached meta-data structure.
	 * 
	 * @return an empty data set cached meta-data structure.
	 */
	public static CachedMetaData createCachedMetaData( )
	{
		return new CachedMetaData( );
	}
	/**
	 * Creates an empty computed column structure.
	 * 
	 * @return an empty computed column structure
	 */
	public static ComputedColumn createComputedColumn( )
	{
		return new ComputedColumn( );
	}
	/**
	 * Creates an empty action structure.
	 * 
	 * @return an empty action structure.
	 */
	public static Action createAction( )
	{
		return new Action( );
	}
	/**
	 * Creates an empty config variable structure.
	 *