if ( query instanceof IQueryDefinition )
IResultSet parent = null; if ( !rsets.isEmpty( ) )
	public IResultSet execute( IBaseQueryDefinition query )	{		if ( query instanceof IQueryDefinition )		{			return doExecuteQuery( query );		}		else if ( query instanceof ISubqueryDefinition )		{			return doExecuteSubQuery( query );		}		return null;	}