Bug 200755 [smoke]Fail to preview Crosstab after deploy BIRT in application servers.[0601][1102]
data/org.eclipse.birt.report.data.adapter/src/org/eclipse/birt/report/data/adapter/api/DataRequestSession.java
* data
	 * 
	 * @param dataSource,
	 *            which is associated with the data set
	 * @param dataSet,
	 *            which cache needs to be cleared
	 * @throws BirtException
	 */
	public abstract void clearCache( IBaseDataSourceDesign dataSource,
			IBaseDataSetDesign dataSet ) throws BirtException;
	/**
	 * This method will return NULL if the named data set is not cached. Otherwise, it
	 * will return an IResultMetaData instance which provides at least the ColumnName
	 * and ColumnType information for all cached columns.
	 * 
	 * Please note that the ParameterHint information will usually essential to the result of data set design is
	 * omitted for it has nothing to do with the metadata.
	 * @param dataSource
	 * @param dataSet
	 * @return
	 * @throws BirtException
	 */
	abstract public IResultMetaData getCachedDataSetMetaData( IBaseDataSourceDesign dataSource,
                   IBaseDataSetDesign dataSet ) throws BirtException;
	
	/**
	 * Shuts down this session, and releases all associated resources.
	 */
	public abstract void shutdown( );
}