Electronic Data Interchange
The Interchange Trailer (UN/EDIFACT)

The Interchange Trailer ends transmission of an interchange.  It contains:

• the number of functional groups encapsulated in the interchange envelope, and
• the matching control number of associated interchange header pair.

This topic covers:

• Interchange Trailer in a Document
• Programmatically Reading the Interchange Trailer
• Programmatically Generating the Interchange Trailer

Interchange Trailer in a document

In the document the interchange trailer is identifier by it segment identifier "UNZ" followed by the data element separator.

The interchange trailer data stream fit into the implementation guideline defined for the interchange trailer as follows:

REF	ELE	NAME	REQ	TYPE	MIN/MAX	VALUE	COMMENT
01	0036	Interchange Control Count	M	N	1/6	1	This value indicates the number of messages that are enveloped by the interchange at the time that it was prepared.
02	0020	Interchange Control Reference	M	AN	1/14	1	This is the control number that associates the interchange trailer with its interchange header pair that has a matching control number.

Programmatically Reading the Interchange Trailer

The following steps demonstrates how to read the interchange trailer.

• Create an instance of ediDocument.

  Dim oEdiDoc As Fredi.ediDocument

  Set oEdiDoc = New Fredi.ediDocument
  

• Load the schema.

  Dim oSchemas As Fredi.ediSchemas
  Dim oSchema As Fredi.ediSchema
  
  ' Disable standard reference library.
  Set oSchemas = oEdiDoc.GetSchemas
  oSchemas.EnableStandardReference = False
  
  Set oSchema = oEdiDoc.LoadSchema(App.Path & "\EDIFACT_INVOIC.SEF", Schema_Standard_Exchange_Format)

• Load the document.

  ' Load EDI document normally.
  oEdiDoc.LoadEdi App.Path & "\SampleEdifactDoc.X12"
  
  

• Get the first interchange.

  Dim oInterchange As Fredi.ediInterchange
  
  ' Get first interchange.
  Set oInterchange = oEdiDoc.FirstInterchange
  
  

• Get the interchange trailer and read elements

  ' Get interchange header.
  Dim oTrailer As Fredi.ediDataSegment
  Dim oElements As Fredi.ediDataElements
  Dim oElement As Fredi.ediDataElement
  Dim sResult As String
  Dim i As Integer
  
  Set oTrailer = oInterchange.GetDataSegmentTrailer
  
  ' Get elements collection.
  Set oElements = oTrailer.DataElements
  
  sResult = ""
  
  For Each oElement In oElements
  

  Dim oSubElements As Fredi.ediDataElements
  Dim oSubElement As Fredi.ediDataElement
  
  Set oSubElements = oElement.DataElements
  
  If oSubElements.Count > 0 Then

  ' Read component elements.
  sResult = sResult & vbTab & oElement.ID & vbCrLf
  
  For Each oSubElement In oSubElements

  sResult = sResult & vbTab & vbTab & oSubElement.ID & " = " & oSubElement.Value & vbCrLf
  
  

  Next
  
  

  Else

  sResult = sResult & vbTab & oElement.ID & " = " & oElement.Value & vbCrLf
  
  

  End If
  

  Next
  

Programmatically Generating the Interchange Trailer

The following steps demonstrates how to generate the interchange header.

• Create an instance of ediDocument.

  Dim oEdiDoc As Fredi.ediDocument

  Set oEdiDoc = New Fredi.ediDocument
  

• Load the schema.

  Dim oSchemas As Fredi.ediSchemas
  Dim oSchema As Fredi.ediSchema
  
  ' Disable standard reference library.
  Set oSchemas = oEdiDoc.GetSchemas
  oSchemas.EnableStandardReference = False
  
  Set oSchema = oEdiDoc.LoadSchema(App.Path & "\EDIFACT_INVOIC.SEF", Schema_Standard_Exchange_Format)

• Specify the terminators.

  ' Specify the terminators to use on the document.
  oEdiDoc.SegmentTerminator = "'" & vbCrLf
  oEdiDoc.ElementTerminator = "+"
  oEdiDoc.CompositeTerminator = ":"
  oEdiDoc.ReleaseIndicator = "?"

• Create the interchange.  The CreateInterchange method creates the interchange entity including the interchange header and trailer control segment.

  Dim oInterchange As Fredi.ediInterchange
  
  ' Create the Interchange envelope.
  Set oInterchange = oEdiDoc.CreateInterchange("UN", "D96A")
  
  

• Set the values in the interchange trailer.  Although the values of the elements in the interchange trailer can be modified, it is not necessary.  The values are automatically populated with the correct values when the document is saved.

  Dim oTrailer As Fredi.ediDataSegment
  
  ' Get the interchange header.
  Set oTrailer = oInterchange.GetDataSegmentTrailer
  
  ' Set the values of the elements.