Bug 179737 The MeasureHandle should be able to provide data type info
We are now allow user input expression as measure expression. However this brings difficulties in determine the data type of a measure expression evaluation result. We need MeasureHandle to be enhanced to include the data type info. Please note that data type "any" is not accepted.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/writer/ModuleWriter.java
super.visitJointDataSet( obj );
		writeStructureList( obj, IDataSetModel.PARAMETERS_PROP );
		writeStructureList( obj, IDataSetModel.RESULT_SET_PROP );
		writeSimplePropertyList( obj, IJointDataSetModel.DATA_SETS_PROP );
		writeStructureList( obj, IJointDataSetModel.JOIN_CONDITONS_PROP );
		writer.endElement( );
	}
	/**
	 * Visits the designer state of the oda data set.
	 * 
	 * @param obj
	 *            the oda data set to traverse
	 */
	private void writeOdaDesignerState( DesignElement obj, String propName )
	{
		OdaDesignerState designerState = (OdaDesignerState) obj
				.getLocalProperty( getModule( ), propName );
		if ( designerState == null )
			return;
		writer.startElement( DesignSchemaConstants.STRUCTURE_TAG );
		writer.attribute( IDesignElementModel.NAME_PROP,
				IOdaDataSetModel.DESIGNER_STATE_PROP );
		property( designerState, OdaDesignerState.VERSION_MEMBER );
		property( designerState, OdaDesignerState.CONTENT_AS_STRING_MEMBER );
		try
		{
			if ( designerState.getContentAsBlob( ) != null )
			{
				byte[] data = base.encode( designerState.getContentAsBlob( ) );
				String value = new String( data, OdaDesignerState.CHARSET );