Delimiters

Goal:

EDI documents are flat file documents that have certain delimiters that separate data elements and segments. Unlike XML which has self describing nodes, EDI documents have to follow strict rules regarding the position of these delimiters for them to be parsed correctly. This blog post is intended to provide an in depth analysis of the various delimiters found in an EDI document, and how R2 Engine discovers these delimiters during disassembly.

X12:

The X12 standard defines the following delimiters that are discovered through the fixed length ISA segment according to the following algorithm:

• Data Element Separator: 4 Char of ISA denotes data element separator. Used to separate simple data element or composite data structure. Commonly used is *
• Component Element Separator: ISA16 denotes this separator. Used to separate simple data elements within a composite data structure. Commonly used is :
• Repetition Separator: ISA11 is reused to denote repetition separator. Used to separate repeated occurrences of a simple data element or a composite data structure. Commonly used is ^
  • Note: Cross verification with PAM settings needs to be conducted to verify usage of ISA11 for this delimiter. If ISA11 is not configured as repetition separator in PAM, then there can be NO repetitions with the fields.
• Segment Separator: 106^th Char of ISA (fixed length segment) denotes segment separator. Used to separate segments. Commonly used is ~
• Segment Separator Suffix: The value present between ISA and the following GS segment. Used to provide better readability for the Interchange. R2 supports “None”, “CR”, “LF” and “CR LF”

Example:

The following ISA and GS segment illustrates the above

ISA*00*00000ISA02*00*11111ISA04*01*2222222222ISA06*01*3333333333ISA08*670123*0123*^*00401*111121891*0*I*:~

GS*AA*GS02*GS03*45670123*01234567*892*X*00306~

In the above example:

• Data Element Separator = “*” (4th Char of ISA)
• Component = “:” (ISA 16)
• Repetition = “^” (ISA 11)
• Segment = “~” (106th char of ISA)
• Segment Suffix = “CR LF”

  

EDIFACT:

EDIFACT has an entire segment dedicated to defining the separators. And as expected this is the first segment and is called UNA, Service String Advice. Its function is to define the characters selected for use as delimiters and indicators in the rest of the interchange that follows. When transmitted, the UNA will appear immediately before the Interchange Header (UNB) segment and begin with the upper case characters UNA immediately followed by the six characters selected by the sender to indicate the applicable separators, in sequence.

Sample Segment: UNA:+.?*’

In the above stream

• The fourth character ‘:’ is the Component element separator
• The fifth character ‘+’ is the Data Element Separator
• The sixth character ‘.’ is the Decimal Notation
• The seventh character ‘?’ is the Release Character
• The eight character ‘*’ is the Repetition Char
• The ninth character ‘’’ is the Segment Separator
• The character between UNA and UNB is used to Segment Separator Suffix. Like X12, R2 supports “None”, “CR”, “LF” and “CR LF” for EDIFACT as well

Exception Handling:

• UNA is an optional string – so if in an interchange this segment is not present than the default values from the Pipeline component properties are used. If these are not valued than the interchange is suspended and appropriately logged in Event Viewer
• Some users don’t use Release indicators in the payload and consequently don’t value it in UNA segment. The standard requires that if not present – space character will be inserted. Importantly space is not be interpreted as the Release indicator. Space char indicates that releasing is not supported in the interchange.

Pipeline Component Properties:

• The highlighted section of the EDI Receive Pipeline is used for EDIFACT documents in case UNA segment is not present in the interchange. The format is Comma Separated Values as Hex Chars in the order (Component Data Element, Data Element, Decimal Notation, Release Indicator, Repetition Separator, Segment Separator, Suffix 1, and Suffix 2)
• The default EDIFACT Separators are 0×3A, 0×2B, 0×2C, 0×3F, 0×20, 0×27
• These values can be configured to any values provided they are in the allowed range and follow the format as described above.

Allowed Range:

Both X12 and EDIFACT delimiters have to be ASCII characters. That means they fall in the range of 0-127 (Decimal) or 00-7F (HEX)

X12 vs. EDIFACT:

The following table outlines the similarities and differences between X12 and EDIFACT

 

Separator Type	EDIFACT		X12
	Field	Optionality	Field	Optionality
Component Element Separator	UNA1	Mandatory	ISA16	Mandatory
Data Element Separator	UNA2	Mandatory	Implicit – Char preceding ISA1 (4th Char)	Mandatory
Decimal	UNA3	Mandatory	N/A	N/A
Release	UNA4	Mandatory	N/A	N/A
Repetition	UNA5	Mandatory	ISA11	Optional
Segment (along with 2 optional suffix field)	UNA6	Mandatory	Implicit – Char following ISA16 (106th Char)	Required

End Note:

I hope this post has been useful to you. As always your comments/questions are welcome. This is mohsin signing off!

Mohsin Kalam