如上圖所示，CDXLOperator作為Base class for operators in a DXL tree，其子類CDXLLogical、CDXLScalar、CDXLPhysical作為邏輯節點、物理節點和Scalar節點的DXL表示類，因此其包含了這些類的共同部分特性，比如獲取其DXL節點表示的函數GetDXLOperator、獲取其Operator類型的函數GetDXLOperatorType，如下圖右側所示。

class CDXLOperator : public CRefCount {
private:	CDXLOperator(const CDXLOperator &); // private copy constructor
protected:	CMemoryPool *m_mp; // memory pool
public:	explicit CDXLOperator(CMemoryPool *); // ctor/dtorvirtual ~CDXLOperator();	virtual Edxlopid GetDXLOperator() const = 0; // ident accessors	virtual const CWStringConst *GetOpNameStr() const = 0; // name of the operatorvirtual Edxloptype GetDXLOperatorType() const = 0;// serialize operator in DXL format given a serializer object and the// host DXL node, providing access to the operator's childrenvirtual void SerializeToDXL(CXMLSerializer *, const CDXLNode *) const = 0;// check if given column is defined by operatorvirtual BOOL IsColDefined(ULONG	 // colid ) const { // by default, operator does not define columnsreturn false;}static const CWStringConst *GetJoinTypeNameStr(EdxlJoinType);	static const CWStringConst *GetIdxScanDirectionStr(EdxlIndexScanDirection); // Return the index scan direction
};

其中最重要的函數是SerializeToDXL，該函數用于使用給定serializer object將operator序列化成DXL format。而GetOpNameStr函數則是獲取該operator DXL類在DXL format中的標簽，其實就是xml中的標簽，如下代碼所示，CDXLScalarAggref的標簽為CDXLTokens::GetDXLTokenStr(EdxltokenScalarAggref)，即為AggFunc。

const CWStringConst *CDXLScalarAggref::GetOpNameStr() const{return CDXLTokens::GetDXLTokenStr(EdxltokenScalarAggref);
}{EdxltokenScalarAggref, GPOS_WSZ_LIT("AggFunc")},

operators in a DXL tree僅僅是DXL tree中的一部分，除了Operator DXL節點的標簽，還有其他標簽，比如Comment、Plan、Id等。