很菜的問題﹐大家幫忙指點﹗﹗﹗﹗﹗﹗﹗﹗﹗﹗﹗(也許比較難)

有如下程序代碼﹕
宣告﹕
----------------------------------------------
Dim oWfDoc As DOMDocument
Dim oFlowModel As IXMLDOMElement
Dim oCfgDoc As DOMDocument
Dim oUsersInfo As DOMDocument
----------------------------------------------
Sub 上載流程資料()

On Error GoTo ErrorHandler

Set oWfDoc = New DOMDocument
Set oFlowModel = oWfDoc.createElement("flowModel")
oWfDoc.appendChild oFlowModel

'Visio的物件宣告
'Pages collection of document
Dim pagsObj As Visio.Pages

'Page to work on
Dim pagObj As Visio.Page
...
------------------------------------------
1.請問DOMDocument是個什么東西? 如何來的﹐我查不到
2.IXMLDOMElement是個什么東西? 如何來的﹐我也查不到
3.Set oFlowModel = oWfDoc.createElement("flowModel")是何意思?
4. oWfDoc.appendChild oFlowModel是何意思?
5.Dim pagsObj As Visio.Pages , VB中可以這樣寫嗎? Visio.pages在哪里來的